Cleanup mountpoint and metadata after running functional tests

Change-Id: I32af81a3000b24e0d7be235becee212dd800dd2f
Signed-off-by: Prashanth Pai <ppai@redhat.com>
Reviewed-on: http://review.gluster.org/5598
Reviewed-by: Luis Pabon <lpabon@redhat.com>
Tested-by: Luis Pabon <lpabon@redhat.com>