Don't signal on updates from muted threads.

Fixes #3393
// FREEBIE

src/org/thoughtcrime/securesms/notifications/MessageNotifier.java

@@ -124,10 +124,16 @@ public class MessageNotifier {
   }
 
   public static void updateNotification(Context context, MasterSecret masterSecret, long threadId) {
-    if (!TextSecurePreferences.isNotificationsEnabled(context)) {
+    Recipients recipients = DatabaseFactory.getThreadDatabase(context)
+                                           .getRecipientsForThreadId(threadId);
+
+    if (!TextSecurePreferences.isNotificationsEnabled(context) ||
+        (recipients != null && recipients.isMuted()))
+    {
       return;
     }
 
+
     if (visibleThread == threadId) {
       ThreadDatabase threads = DatabaseFactory.getThreadDatabase(context);
       threads.setRead(threadId);