Return correct status when deleting non-existing container

The code was raising an exception when the container (which
happens to be a directory) did not exist.  To be compatible
with OpenStack Swift, we need to handle an object which its
container/directory does not exist.

BUG: 960944 (https://bugzilla.redhat.com/show_bug.cgi?id=960944)

Change-Id: Ibb2db354a655e040fb70ebbe6a7d8f815d33dc0f
Signed-off-by: Luis Pabon <lpabon@redhat.com>
Reviewed-on: http://review.gluster.org/5201
Reviewed-by: Peter Portante <pportant@redhat.com>
Tested-by: Peter Portante <pportant@redhat.com>