Summary:
After https://github.com/facebook/rocksdb/pull/7036, we still see extra DBTest that can timeout when running 10 or 20 in parallel. Expand skip-fsync mode in whole DBTest. Still preserve other tests from doing this mode to be conservative.

This commit reinstates https://github.com/facebook/rocksdb/issues/7049, whose un-revert was lost in an automatic
infrastructure mis-merge.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7274

Test Plan: Run all existing files.

Reviewed By: pdillinger

Differential Revision: D23177444

fbshipit-source-id: 1f61690b2ac6333c3b2c87176fef6b2cba086b33