Don't connect to server if !isPushRegistered

Partial fix for #6620.
Closes #6627
// FREEBIE

src/org/thoughtcrime/securesms/service/MessageRetrievalService.java

@@ -144,7 +144,8 @@ public class MessageRetrievalService extends Service implements InjectableType,
     Log.w(TAG, String.format("Network requirement: %s, active activities: %s, push pending: %s, gcm disabled: %b",
                              networkRequirement.isPresent(), activeActivities, pushPending.size(), isGcmDisabled));
 
-    return TextSecurePreferences.isWebsocketRegistered(this)                  &&
+    return TextSecurePreferences.isPushRegistered(this)                       &&
+           TextSecurePreferences.isWebsocketRegistered(this)                  &&
            (activeActivities > 0 || !pushPending.isEmpty() || isGcmDisabled)  &&
            networkRequirement.isPresent();
   }