nfsd: shut down the NFSv4 state objects before the filecache

[ Upstream commit 789e1e10

 ]

Currently, we shut down the filecache before trying to clean up the
stateids that depend on it. This leads to the kernel trying to free an
nfsd_file twice, and a refcount overput on the nf_mark.

Change the shutdown procedure to tear down all of the stateids prior
to shutting down the filecache.

Reported-and-tested-by: Wang Yugui <wangyugui@e16-tech.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Fixes: 5e113224

 ("nfsd: nfsd_file cache entries should be per net namespace")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>