Summary:
Fix an intermittent failure in
DBErrorHandlingTest.CompactionManifestWriteError due to a race between
background error recovery and the main test thread calling
TEST_WaitForCompact().
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6367

Test Plan: Run the test using gtest_parallel

Differential Revision: D19713802

Pulled By: anand1976

fbshipit-source-id: 29e35dc26e0984fe8334c083e059f4fa1f335d68