[PATCH] nfsd4: rename lk_stateowner

One of the things that's confusing about nfsd4_lock is that the lk_stateowner
field could be set to either of two different lockowners: the open owner or
the lock owner.  Rename to lk_replay_owner and add a comment to make it clear
that it's used for whichever stateowner has its sequence id bumped for replay
detection.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>