Summary:
stop calling Close() at the end of tests holding a compaction pressure token since it causes the write controller to be deleted while it's still needed. these calls were pointless anyways since Close() is already called in the test's destructor.
Closes https://github.com/facebook/rocksdb/pull/2367

Differential Revision: D5125906

Pulled By: ajkr

fbshipit-source-id: 6cad8673e5546a82ff602ac0ba59cc3f68dbde46