dlm: remove unnecessary INIT_LIST_HEAD()

There is no need to call INIT_LIST_HEAD() when it's set directly
afterwards by list_add_tail().

Reported-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>