nfs-utils: don't use signals to shut down nfs server.

Since Linux v2.4 it has been possible to stop all NFS server by running

   rpc.nfsd 0

i.e.  by requesting that zero threads be running.  This is preferred as
it doesn't risk killing some other process which happens to be called
"nfsd".

Since Linux v6.6 - and other stable kernels to which

  Commit: 390390240145 ("nfsd: don't allow nfsd threads to be
  signalled.")

has been backported - sending a signal no longer works to stop nfs server
threads.

This patch changes the nfsserver script to use "rpc.nfsd 0" to stop
server threads.

(From OE-Core rev: 415e73d53e5342f3f6ff6acd521ded2df3fbca1f)

Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 7b09ad289a36)
Signed-off-by: Haixiao Yan <haixiao.yan.cn@windriver.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

meta/recipes-connectivity/nfs-utils/nfs-utils/nfsserver

@@ -66,34 +66,14 @@ start_nfsd(){
 	start-stop-daemon --start --exec "$NFS_NFSD" -- "$@"
 	echo done
 }
-delay_nfsd(){
-	for delay in 0 1 2 3 4 5 6 7 8 9 
-	do
-		if pidof nfsd >/dev/null
-		then
-			echo -n .
-			sleep 1
-		else
-			return 0
-		fi
-	done
-	return 1
-}
 stop_nfsd(){
-	# WARNING: this kills any process with the executable
-	# name 'nfsd'.
 	echo -n 'stopping nfsd: '
-	start-stop-daemon --stop --quiet --signal 1 --name nfsd
-	if delay_nfsd || {
-		echo failed
-		echo ' using signal 9: '
-		start-stop-daemon --stop --quiet --signal 9 --name nfsd
-		delay_nfsd
-	}
+	$NFS_NFSD 0
+	if pidof nfsd
 	then
-		echo done
-	else
 		echo failed
+	else
+		echo done
 	fi
 }