Summary:
1. Fix a memory leak in FaultInjectionTestFS in the stack trace related
code
2. Check status of all MultiGet keys before deciding whether an error
was swallowed, instead of assuming an ok status for any key means an
undetected error
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6700
Test Plan: Run db_stress with asan and fault injection
Reviewed By: cheng-chang
Differential Revision: D21021498
Pulled By: anand1976
fbshipit-source-id: 489191efd1ab0fa834923a1e1d57253a7a315465
234e2ed5b6