nfsd4: fix FREE_STATEID lockowner leak

commit 48385408b45523d9a432c66292d47ef43efcbb94 upstream.

27b11428b7de ("nfsd4: remove lockowner when removing lock stateid")
introduced a memory leak.

Reported-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>