Stop GC and SServers first when stopping cluster (apache#5396)

* Stop GC and SServers first when stopping cluster

The GC and Scan Server processes can put a load onto the
metadata table with scan and writes. This activity could
hold up metadata tablet unloading. These processes aren't
necessary for an orderly shutdown, so they can be shut
down first.

* Removed duplicate local declarations

Author: dlmarion

assemble/bin/accumulo-cluster

@@ -482,9 +482,29 @@ function control_services() {
   local group
   local tserver
   local G
+  local sserver
+  local gc
   if [[ $ARG_ALL == 1 && $ARG_LOCAL == 0 && $operation == "stop" ]]; then
     echo "Stopping Accumulo cluster..."
     if ! isDebug; then
+      # Stop all of the the Scan Server processes
+      for group in $SSERVER_GROUPS; do
+        echo "Executing $(green "$ARG_CMD") on $(purple scan servers) for group $(yellow "$group")"
+        hosts="SSERVER_HOSTS_$group"
+        for sserver in ${!hosts}; do
+          if canRunOnHost "$sserver"; then
+            execute_command "$operation" "$sserver" sserver "$group" "-g" "$group"
+          fi
+        done
+      done
+      # Stop the GC processes, they scan and write to the metadata table
+      for gc in $GC_HOSTS; do
+        if canRunOnHost "$gc"; then
+          echo "Executing $(green "$ARG_CMD") on $(purple garbage collectors)"
+          execute_command "$operation" "$gc" gc "default"
+        fi
+      done
+      # Try to cleanly stop the TabletServers and Manager
       if ! "$accumulo_cmd" admin stopAll; then
         echo "Invalid password or unable to connect to the manager"
         echo "Initiating forced shutdown in 15 seconds (Ctrl-C to abort)"
@@ -559,7 +579,6 @@ function control_services() {
     done
   fi
 
-  local gc
   if [[ $ARG_ALL == 1 || $ARG_GC == 1 ]]; then
     for gc in $GC_HOSTS; do
       if canRunOnHost "$gc"; then
@@ -590,7 +609,6 @@ function control_services() {
   fi
 
   local sserver_groups
-  local sserver
   if [[ $ARG_ALL == 1 || $ARG_SSERVER == 1 ]]; then
     sserver_groups=$SSERVER_GROUPS
     if [[ -n $ARG_SSERVER_GROUP ]]; then