ACCUMULO-3320 Update thrift idl
ACCUMULO-3320 Add a new method to the master to get the active tservers
ACCUMULO-3320 Fetch the necessary info from the master and tservers in the GC
ACCUMULO-3320 Use the active WALs from each tserver to preclude WAL deletion
ACCUMULO-3320 Normalize the WAL using Path.
ACCUMULO-3320 Integration test to ensure that WALs are not closed when a tserver may continue to use it.

Also test for the converse that after a WAL is unused by a tserver, it is still closed.
ACCUMULO-3320 Some cleanup and add IT suffix to test name.
ACCUMULO-3320 Stabilize the test after a noticed failure.
ACCUMULO-3320 At "IT" suffix to integration test.
ACCUMULO-3320 Fix up whitespace formatting.