features/quota: fix the dict leak when quota is off

Change-Id: I15036da90e96b69858eac5a19bd438df3bd8cc53
BUG: 1075506
Signed-off-by: Varun Shastry <vshastry@redhat.com>
Reviewed-on: http://review.gluster.org/7233
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>