Correctly close old nfsd/lockd sockets.

Commit aaf68cfb

 added a bias
to sk_inuse, so this test for an unused socket now fails.  So no
sockets get closed because they are old (they might get closed
if the client closed them).

This bug has existed since 2.6.21-rc1.

Thanks to Wolfgang Walter for finding and reporting the bug.

Cc: Wolfgang Walter <wolfgang.walter@studentenwerk.mhn.de>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>