nightly test polish

[leftwo]

Updates to the nightly tests and the tests it calls.

All the nightly tests have their own named directory for test logs

WORK_ROOT=${WORK_ROOT:-/tmp}
TEST_ROOT="$WORK_ROOT/<test_name>"

This makes cleanup at the end easier.
In all tests, dsc now logs to this or a specified directory.

All the nightly tests now have a REGION_ROOT, and this is where dsc or the crucible downstairs will create region directories. This makes it easier for the caller to direct the tests to use a specific location instead of everyone piling in to /var/tmp

If a test finishes without error, it will clean up logs and regions that were created as part of the test. If there is an error, then we leave things behind. We clean up the contents of REGION_ROOT but only what each test creates itself.

Updated tools/test_nightly.sh to print the name of the test it is running, and just cleaned up the output a bit.

[mkeeter]

Are there cases where this wouldn't be empty? If not, should we do rm -r "$REGION_ROOT" versus deleting region dirs individually?

[leftwo]

So, what I want here was something I don't think this is going to give me, and you are
right to call out what this half measure was doing.

What I want is for the caller to be able to supply a directory and have this (and any
other tests) use that directory as a place where the regions are created.
The problem arises if that directory is not empty. I don't want this test to blindly
destroy whatever exists. My half measure was to only remove directories that I
knew this tests created.

However, I now think a better solution is to, like we do with TEST_ROOT, is to create
a specific subdirectory inside REGION_ROOT, and put all region directories inside that.

This way I can always remove $REGION_ROOT/<my_test_unique_subdir> and not have
to care what is in that directory, or even know what exact directories exist inside it, which
will be a problem when I make these tests have multiple region sets.

I'll refactor this and all the places where we use REGION_ROOT

[leftwo]

This is wrong, and should be MY_REGION_ROOT=${REGION_ROOT}/hammer_loop
Should be fixed in newer commits.