nfsd: return correct lockowner when there is a race on hash insert

nfsd: return correct lockowner when there is a race on hash insert

[ Upstream commit 340f0ba1c6c8412aa35fd6476044836b84361ea6 ]

alloc_init_lock_stateowner can return an already freed entry if there is
a race to put openowners in the hashtable.

Noticed by inspection after Jeff Layton fixed the same bug for open
owners.  Depending on client behavior, this one may be trickier to
trigger in practice.

Fixes: c58c6610ec24 "nfsd: Protect adding/removing lock owners using client_lock"
Cc: <stable@vger.kernel.org>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Acked-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>