mwan3: fix race condition on mwan3 restart

This adjustment of the locks fixes the race condition when a mwan3
hotplug script and a mwan3 command are running at the same time.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>
(cherry picked from commit 2dac1bcdc9)

net/mwan3/files/etc/hotplug.d/iface/16-mwan3-user

@@ -2,13 +2,25 @@
 
 [ -f "/etc/mwan3.user" ] && {
 	. /lib/functions.sh
+	. /lib/mwan3/mwan3.sh
+
+	mwan3_lock "$ACTION" "user"
 
 	config_load mwan3
 	config_get_bool enabled globals 'enabled' '0'
-	[ ${enabled} -gt 0 ] || exit 0
+	[ ${enabled} -gt 0 ] || {
+		mwan3_unlock "$ACTION" "user"
+		exit 0
+	}
 
 	config_get enabled "$INTERFACE" enabled 0
-	[ "${enabled}" = "1" ] || exit 0
+	[ "${enabled}" = "1" ] || {
+		mwan3_unlock "$ACTION" "user"
+		exit 0
+	}
+
+	mwan3_unlock "$ACTION" "user"
+
 	env -i ACTION="$ACTION" INTERFACE="$INTERFACE" DEVICE="$DEVICE" \
 		/bin/sh /etc/mwan3.user
 }