ocfs2: initialize stack_user lvbptr

The locking_state dump, ocfs2_dlm_seq_show, reads the lvb on locks where it
has not yet been initialized by a lock call.

Signed-off-by: David Teigland <teigland@redhat.com>
Acked-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>