Quota count can go wrong when double buffer flush takes time

Quota count can go wrong in below scenario,

1. DirectoryDeletingService submitted task to purge directory and is completed
2. Double buffer is taking time

This is as deletedDirectoryTable is read for creating purge list in DirectoryDeletingService. currently in-progress check is not done.

So multiple time, same directory being deleted with sub-dir and sub-files, causing quota keeps reducing during purge.