Cleanup of ThreadStatusUtil structures should use the DB's reference

Cleanup of ThreadStatusUtil structures should use the DB's reference

Summary:
instead of thread_local

The cleanup path for the rocksdb database might not have the
thread_updater_local_cache_ pointer initialized because the thread
executing the cleanup is likely not a rocksdb thread. This results in a
memory leak detected by Valgrind. The cleanup code path should use the
thread_status_updater pointer obtained from the DB object instead of a
thread local one.
Closes https://github.com/facebook/rocksdb/pull/2059

Differential Revision: D4801611

Pulled By: hermanlee

fbshipit-source-id: 407d7de