NFS/localio: nfs_close_local_fh() fix check for file closed

If the struct nfs_file_localio is closed, its list entry will be empty,
but the nfs_uuid->files list might still contain other entries.

Acked-by: Mike Snitzer <snitzer@kernel.org>
Tested-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: NeilBrown <neil@brown.name>
Fixes: 21fb4403 ("nfs_localio: protect race between nfs_uuid_put() and nfs_close_local_fh()")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>