[DLM] move kmap to after spin_unlock

Doing the kmap() while holding the spinlock was causing recursive spinlock
problems.  It seems the kmap was scheduling, although there was no warning
as I'd expect.  Patrick, do we need locking around the kmap?

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>