Fix DNS route not cleaned

mobile/src/main/java/be/mygod/vpnhotspot/net/Routing.kt

@@ -298,6 +298,7 @@ class Routing(private val caller: Any, private val downstream: String) : IpNeigh
         Timber.i("Stopped routing for $downstream by $caller")
         TrafficRecorder.update()    // record stats before exiting to prevent stats losing
         clients.values.forEach { it.close() }
+        currentDns?.transaction?.revert()
         fallbackUpstream.subrouting?.transaction?.revert()
         upstream.subrouting?.transaction?.revert()
         transaction.revert()