mwan3: make it clearer who initiated the start

It was somewhat opaque how the variable a is questioned. To show this
better the variable is now a string and not a boolean. So you can see
directly what should happen. With a boolean you always have to think
about what it means when 0 or 1 is used.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>

net/mwan3/files/usr/sbin/mwan3

@@ -54,7 +54,7 @@ ifup() {
 		exit 0
 	fi
 
-	mwan3_ifup "$1"
+	mwan3_ifup "$1" "cmd"
 }
 
 interfaces()