Summary:
Updated stress test will support testing of db in read-only mode.
The user has to make sure that only read/scan operations are enabled.
This PR relies on #4681.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4690
Differential Revision: D13102741
Pulled By: riversand963
fbshipit-source-id: f5a36b34db187fe12dd355f7eda161f99d6c75e4