Revert "Ensure receiver unregistered synchronously in onDestroy"

This reverts commit e55aa17399.

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

@@ -10,7 +10,6 @@ import be.mygod.vpnhotspot.net.TetheringManager.tetheredIfaces
 import be.mygod.vpnhotspot.net.monitor.IpNeighbourMonitor
 import be.mygod.vpnhotspot.util.Event0
 import be.mygod.vpnhotspot.util.broadcastReceiver
-import be.mygod.vpnhotspot.util.ensureReceiverUnregistered
 import kotlinx.coroutines.*
 import java.util.concurrent.ConcurrentHashMap
 
@@ -47,6 +46,7 @@ class TetheringService : IpNeighbourMonitoringService(), CoroutineScope {
     override val coroutineContext = dispatcher + Job()
     private val binder = Binder()
     private val downstreams = ConcurrentHashMap<String, Downstream>()
+    private var receiverRegistered = false
     private val receiver = broadcastReceiver { _, intent ->
         launch {
             val toRemove = downstreams.toMutableMap()   // make a copy
@@ -69,8 +69,11 @@ class TetheringService : IpNeighbourMonitoringService(), CoroutineScope {
             ServiceNotification.stopForeground(this)
             stopSelf()
         } else {
-            registerReceiver(receiver, IntentFilter(TetheringManager.ACTION_TETHER_STATE_CHANGED))
-            IpNeighbourMonitor.registerCallback(this)
+            if (!receiverRegistered) {
+                receiverRegistered = true
+                registerReceiver(receiver, IntentFilter(TetheringManager.ACTION_TETHER_STATE_CHANGED))
+                IpNeighbourMonitor.registerCallback(this)
+            }
             updateNotification()
         }
         launch(Dispatchers.Main) { binder.routingsChanged() }
@@ -103,9 +106,9 @@ class TetheringService : IpNeighbourMonitoringService(), CoroutineScope {
     }
 
     override fun onDestroy() {
-        unregisterReceiver()
         launch {
             downstreams.values.forEach { it.destroy() } // force clean to prevent leakage
+            unregisterReceiver()
             cancel()
             dispatcher.close()
         }
@@ -113,7 +116,10 @@ class TetheringService : IpNeighbourMonitoringService(), CoroutineScope {
     }
 
     private fun unregisterReceiver() {
-        ensureReceiverUnregistered(receiver)
-        IpNeighbourMonitor.unregisterCallback(this)
+        if (receiverRegistered) {
+            unregisterReceiver(receiver)
+            IpNeighbourMonitor.unregisterCallback(this)
+            receiverRegistered = false
+        }
     }
 }