Simplify nfsd4_release_lockowner a bit, factor out code that we need for
another patch.

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