Replace strict mode with fallback upstream interface

Fixes #40. Apparently we can no longer take advantage of default network rules set by Android system since Android 9.0 thanks to this commit: 758627c4d9

mobile/src/main/java/be/mygod/vpnhotspot/LocalOnlyHotspotService.kt

@@ -44,7 +44,7 @@ class LocalOnlyHotspotService : IpNeighbourMonitoringService() {
         } else {
             val routingManager = routingManager
             if (routingManager == null) {
-                this.routingManager = LocalOnlyInterfaceManager(this, iface)
+                this.routingManager = LocalOnlyInterfaceManager(iface)
                 IpNeighbourMonitor.registerCallback(this)
             } else check(iface == routingManager.downstream)
         }