Summary:
Two TSAN tests occaionaly fail. Exclude them for now:

[ RUN      ] DeleteFileTest.BackgroundPurgeCFDropTest
db/deletefile_test.cc:122: Failure
Expected equality of these values:
  required_manifest
    Which is: 1
  manifest_cnt
    Which is: 2

[ RUN      ] FormatLatest/ColumnFamilyTest.FlushCloseWALFiles/0
db/column_family_test.cc:3004: Failure
Expected equality of these values:
  2
  env.num_open_wal_file_.load()
    Which is: 1

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7152

Test Plan: Watch CircleCI restuls

Reviewed By: ajkr

Differential Revision: D22632285

fbshipit-source-id: 29fa348e8be917be0237c74812a8b0b04978e84e