Summary:
Fix the deadlock issue in ThreadStatusSingleCompaction.
In the previous version of ThreadStatusSingleCompaction, the compaction
thread will wait for a SYNC_POINT while its db_mutex is held. However,
if the test hasn't finished its Put cycle while a compaction is running,
a deadlock will happen in the test.
Test Plan:
export ROCKSDB_TESTS=ThreadStatus
./db_test
Reviewers: sdong, igor
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D35001