Add ability to distinguish between active commit log file and all other commit log files in CleanupManager

[richardartoul]

Right now, the cleanup manager is unable to distinguish between the active commit log file and other commit log files. This is ok for now because if ever are unable to read the info header of a commit log file, we just ignore it. We'd like to be able to automatically clean up corrupt commit log files in the cleanup manager, but this introduces the issue that a brand new commit log file with an incomplete header is indistinguishable from a corrupt commit log file. As a result of this, we need to expose information about the current commit log file to the cleanup manager in order to facilitate automatic deletion of corrupt files.

[richardartoul]

I'll tackle this in a separate P.R once #1066 lands

[richardartoul]

Also make sure to re-enable the test: TestCleanupManagerDeletesCorruptCommitLogFiles once this is achieved

[richardartoul]

Will be resolved by #1090

[richardartoul]

Closed by #1090