Ensure rescheduleUpdate is ran on bg thread

mobile/src/main/java/be/mygod/vpnhotspot/client/ClientsFragment.kt

@@ -229,8 +229,12 @@ class ClientsFragment : Fragment() {
         super.onStart()
         // we just put these two thing together as this is the only place we need to use this event for now
         TrafficRecorder.foregroundListeners[this] = adapter::updateTraffic
+        lifecycleScope.launchWhenStarted {
+            withContext(Dispatchers.Default) {
                 TrafficRecorder.rescheduleUpdate()  // next schedule time might be 1 min, force reschedule to <= 1s
             }
+        }
+    }
 
     override fun onStop() {
         TrafficRecorder.foregroundListeners -= this