Delete notification channel when possible

Added the notification channel delete method call back into the router service. Some phones like the pixel 2 & 3 were only clearing the notificaiton 5-7 seconds after the service called stopForeground. Deleting the channel removes the notification instantly. We added a check to avoid a race condition in which the channel is deleted before the notifcation was actually shown.

Author: joeygrover

android/sdl_android/src/main/java/com/smartdevicelink/transport/SdlRouterService.java

@@ -69,6 +69,7 @@
 import android.os.ParcelFileDescriptor;
 import android.os.Parcelable;
 import android.os.RemoteException;
+import android.service.notification.StatusBarNotification;
 import android.support.annotation.NonNull;
 import android.support.v4.app.NotificationCompat;
 import android.util.Log;
@@ -1516,6 +1517,27 @@ private void exitForeground(){
 		synchronized (NOTIFICATION_LOCK) {
 			if (isForeground && !isPrimaryTransportConnected()) {	//Ensure that the service is in the foreground and no longer connected to a transport
 				this.stopForeground(true);
+				NotificationManager notificationManager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
+				if (notificationManager!= null && Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+					try {
+						boolean notificationHasDisplayed = false;
+						StatusBarNotification[] notifications = notificationManager.getActiveNotifications();
+						for (StatusBarNotification notification : notifications) {
+							if(notification != null && FOREGROUND_SERVICE_ID == notification.getId()){
+								DebugTool.logInfo("Service notification is being displayed");
+								notificationHasDisplayed = true;
+								break;
+							}
+						}
+						if (notificationHasDisplayed) {
+							notificationManager.deleteNotificationChannel(SDL_NOTIFICATION_CHANNEL_ID);
+						}
+						//else leave the notification channel alone to avoid deleting it before the
+						//foreground service notification has a chance to be displayed.
+					} catch (Exception e){
+						DebugTool.logError("Issue when deleting notification channel", e);
+					}
+				}
 				isForeground = false;
 			}
 		}