dlm: close othercons

This patch addresses a problem introduced with the last round of
lowcomms patches where the 'othercon' connections do not get freed when
the DLM shuts down.

This results in the error message
"slab error in kmem_cache_destroy(): cache `dlm_conn': Can't free all
objects"

and the DLM cannot be restarted without a system reboot.

See bz#428119

Signed-off-by: Patrick Caulfield <pcaulfie@redhat.com>
Signed-off-by: Fabio M. Di Nitto <fabbione@ubuntu.com>
Signed-off-by: David Teigland <teigland@redhat.com>