nfsd: pass proper net to nfsd_destroy() from NFSd kthreads

Since NFSd service is per-net now, we have to pass proper network
context in nfsd_shutdown() from NFSd kthreads.

The simplest way I found is to get proper net from one of transports
with permanent sockets.
Signed-off-by: NStanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfssvc.c

@@ -541,6 +541,8 @@ static int
 nfsd(void *vrqstp)
 {
 	struct svc_rqst *rqstp = (struct svc_rqst *) vrqstp;
+	struct svc_xprt *perm_sock = list_entry(rqstp->rq_server->sv_permsocks.next, typeof(struct svc_xprt), xpt_list);
+	struct net *net = perm_sock->xpt_net;
 	int err;
 
 	/* Lock module and set up kernel thread */
@@ -605,7 +607,7 @@ nfsd(void *vrqstp)
 	/* Release the thread */
 	svc_exit_thread(rqstp);
 
-	nfsd_destroy(&init_net);
+	nfsd_destroy(net);
 
 	/* Release module */
 	mutex_unlock(&nfsd_mutex);