[RHGS] Gluster quota usage calculation is not correct

Issue

I have a two node RHGS cluster with quotas enabled/set on sub-directories within a volume.

The hard-limit was reached on one of the folders, but after cleaning up some files, the hard-limit has not refreshed.

# gluster volume quota test list
Path                   Hard-limit  Soft-limit      Used  Available  Soft-limit exceeded? Hard-limit exceeded?
/directory                                  20.0GB     80%(16.0GB)   20.0GB  0Bytes             Yes                  Yes
# du -sh /bricks/testlv/rhgs/directory
4.0G    /bricks/testlv/rhgs/directory