ocfs2: Move slot map access into slot_map.c

journal.c and dlmglue.c would refresh the slot map by hand.  Instead, have
the update and clear functions do the work inside slot_map.c.  The eventual
result is to make ocfs2_slot_info defined privately in slot_map.c

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>