OOIION-1497 HDF File Locking Cache

This pull request fixes the cache invalidation strategy by the HDF Locking utility. 

Before, if the filesystem had a legitimate lock in-place and a client attempted to acquire the lock, it would make an entry in the cache that it was locked, any subsequent calls to try to lock it would fail because it was cached and there was no invalidation of the cache. 

This change ensures that if the filesystem indicates that the file is locked, then the cache is invalidated. 

This pull request also contains a test to verify that this functionality does in-fact work.