[PATCH] Fix miscompare in __posix_lock_file

 If an application requests the same lock twice, the
 kernel should just leave the existing lock in place.
 Currently, it will install a second lock of the same type.
Signed-off-by: NOlaf Kirch <okir@suse.de>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>