admin fate improvements, LockIDs use for fate stores improved/fixed (apache#5028)

* `admin fate` improvements, `LockID`s use for fate stores improved/fixed

This commit makes several improvements/fixes: improvements to the `admin fate` util which were made possible from apache#4524, replaced incorrect use of `createDummyLockID()` in real code (now only used in tests), `<User/Meta>FateStore` now support a null lock id if they will be used as read-only stores: write ops will fail on a store with a null lock, and some other misc. changes.

Full list of changes:
- Removed the check for a dead Manager in the Admin fate util (AdminUtil) which was checked before `admin fate delete <tx>` or `admin fate fail <tx>` was able to run. This check is no longer needed with the changes from apache#4524. apache#4524 moved reservations out of Manager memory into the FATE table (for UserFateStore) and into ZK (for MetaFateStore). Prior to this, the Admin process would have no way of knowing if the Manager process had a transaction reserved, so the Manager had to be shutdown to ensure it was not. But now that reservations are visible to any process, we can try to reserve the transaction in Admin, and if it cannot be reserved and deleted/failed in a reasonable time, we let the user know that the Manager would need to be shutdown if deleting/failing the transaction is still desired.
	- This has several benefits:
	- It is one less thing to worry about when implementing multiple managers in the future since Admin assumes only one Manager for these commands. However, there is still the case where the Manager may
	keep a transaction reserved for a long period of time and the Admin can never reserve it. In this case, we inform the user that the transaction could not be deleted/failed and that if deleting/failing
	is still desired, the Manager may need to be shutdown.
	- It covers a potential issue in the previously existing code where there was nothing stopping or ensuring a Manager is not started after the check is already performed in Admin but before the delete/
	fail was executed.
	- It also should make the commands easier to use now since the Manager is not required to be shutdown before use.
- Changes and adds some tests for `admin fate fail` and `admin fate delete`: ensures the Manager is not required to be down to fail/delete a transaction, and ensures that if the Manager does have a transaction reserved, admin will fail to reserve and fail/delete the transaction.
- Another change which was needed as a prerequisite for the above changes was creating a ZK lock for Admin so transactions can be properly reserved by the command. Added new constant `Constants.ZADMIN_LOCK = "/admin/lock"`, changed `ServiceLockPaths`, and added `Admin.createAdminLock()` to support this
- New class `TestLock` (in test package) which is used by tests to create a real ZK lock, or a dummy one. Removed `createDummyLockID()` from `AbstractFateStore` (moved to TestLock), and `createDummyLock()` is now only used in test code. Added new constant `ZTEST_LOCK = "/test/lock"`, changed `ServiceLockPaths`, and added `createTestLock()` which is used to create a real lock id (one held in ZK) which is needed for some tests.
	- This fixes an unexpected failure that could have occurred for `ExternalCompaction_1_IT`. Was using a dummy lock for the store before and the fate data was being stored in the same locations that the
	Manager uses for it's fate data. The DeadReservationCleaner running in Manager would have cleaned up reservations created using this store if it ran when reservations were present. Now the test creates
	a real ZK lock so the DeadReservationCleaner won't clean these up unexpectedly.
- Stores now support a null lock id for the situation where they will be used as read-only stores. A store with a null lock id will fail on write ops. Changed all existing uses of stores to only have a lock id if writes will occur (previously, all instances of the stores had a lock id).
- Removed unused or unneccesary constructors for AbstractFateStore, MetaFateStore, UserFateStore
- Ensured all tests changed, all FATE tests, and sunny day tests still pass

closes apache#4904

Author: kevinrr888

core/src/main/java/org/apache/accumulo/core/Constants.java

@@ -88,6 +88,8 @@ public class Constants {
 
   public static final String ZTABLE_LOCKS = "/table_locks";
   public static final String ZMINI_LOCK = "/mini";
+  public static final String ZADMIN_LOCK = "/admin/lock";
+  public static final String ZTEST_LOCK = "/test/lock";
 
   public static final String BULK_PREFIX = "b-";
   public static final String BULK_RENAME_FILE = "renames.json";

core/src/main/java/org/apache/accumulo/core/fate/AbstractFateStore.java

@@ -101,10 +101,6 @@ public FateId newRandomId(FateInstanceType instanceType) {
   // Keeps track of the number of concurrent callers to waitForStatusChange()
   private final AtomicInteger concurrentStatusChangeCallers = new AtomicInteger(0);
 
-  public AbstractFateStore() {
-    this(createDummyLockID(), null, DEFAULT_MAX_DEFERRED, DEFAULT_FATE_ID_GENERATOR);
-  }
-
   public AbstractFateStore(ZooUtil.LockID lockID, Predicate<ZooUtil.LockID> isLockHeld) {
     this(lockID, isLockHeld, DEFAULT_MAX_DEFERRED, DEFAULT_FATE_ID_GENERATOR);
   }
@@ -114,9 +110,7 @@ public AbstractFateStore(ZooUtil.LockID lockID, Predicate<ZooUtil.LockID> isLock
     this.maxDeferred = maxDeferred;
     this.fateIdGenerator = Objects.requireNonNull(fateIdGenerator);
     this.deferred = Collections.synchronizedMap(new HashMap<>());
-    this.lockID = Objects.requireNonNull(lockID);
-    // If the store is used for a Fate which runs a dead reservation cleaner,
-    // this should be non-null, otherwise null is fine
+    this.lockID = lockID;
     this.isLockHeld = isLockHeld;
   }
 
@@ -291,6 +285,10 @@ protected void verifyFateKey(FateId fateId, Optional<FateKey> fateKeySeen,
         "Collision detected for fate id " + fateId);
   }
 
+  protected void verifyLock(ZooUtil.LockID lockID, FateId fateId) {
+    Preconditions.checkState(lockID != null, "Tried to reserve " + fateId + " with null lockID");
+  }
+
   protected abstract Stream<FateIdStatus> getTransactions(EnumSet<TStatus> statuses);
 
   protected abstract TStatus _getStatus(FateId fateId);
@@ -450,14 +448,4 @@ protected static Serializable deserializeTxInfo(TxInfo txInfo, byte[] data) {
       throw new IllegalStateException("Bad node data " + txInfo);
     }
   }
-
-  /**
-   * this is a temporary method used to create a dummy lock when using a FateStore outside the
-   * context of a Manager (one example is testing) so reservations can still be made.
-   *
-   * @return a dummy {@link ZooUtil.LockID}
-   */
-  public static ZooUtil.LockID createDummyLockID() {
-    return new ZooUtil.LockID("/path", "node", 123);
-  }
 }