Summary:
A previous change meant to make db_stress to run on sync=1 mode for 1/20 of the time in crash_test, but a bug caused to to always run on sync=1 mode. Fix it.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6304
Test Plan: Start and kill "python -u tools/db_crashtest.py --simple whitebox" multiple times and observe that most times sync=0 is used while some times sync=1 is used.
Differential Revision: D19433000
fbshipit-source-id: 7a0adba39b17a1b3acbbd791bb0cdb743b91fa95