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

@@ -4,14 +4,17 @@
 . /lib/functions/network.sh
 . /lib/mwan3/mwan3.sh
 
+mwan3_lock "$ACTION" "mwan3rtmon"
+
 config_load mwan3
 config_get_bool enabled globals 'enabled' '0'
-[ ${enabled} -gt 0 ] || exit 0
+[ ${enabled} -gt 0 ] || {
+	mwan3_unlock "$ACTION" "mwan3rtmon"
+	exit 0
+}
 
 if [ "$ACTION" == "ifup" ]; then
-	mwan3_lock "$ACTION" "mwan3rtmon"
 	mwan3_rtmon
-	mwan3_unlock "$ACTION" "mwan3rtmon"
 fi
 
 config_get enabled $INTERFACE enabled 0
@@ -19,4 +22,6 @@ config_get enabled $INTERFACE enabled 0
 	mwan3_flush_conntrack "$INTERFACE" "$ACTION"
 }
 
+mwan3_unlock "$ACTION" "mwan3rtmon"
+
 exit 0