Fix TimedEventManager crash in a sane way.

Follow up on acb48752c.

Just have the subclass call that method to guarantee that everything is
initialized.

src/org/thoughtcrime/securesms/revealable/RevealableMessageManager.java

@@ -32,6 +32,8 @@ public class RevealableMessageManager extends TimedEventManager<RevealExpiration
 
     this.mmsDatabase        = DatabaseFactory.getMmsDatabase(application);
     this.attachmentDatabase = DatabaseFactory.getAttachmentDatabase(application);
+    
+    scheduleIfNecessary();
   }
 
   @WorkerThread

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

@@ -29,10 +29,6 @@ public abstract class TimedEventManager<E> {
 
     this.application = application;
     this.handler     = new Handler(handlerThread.getLooper());
-
-    // XXX Have to delay it because some devices will run the resulting handler#post synchronously,
-    //     triggering a method call to an uninitialized child class.
-    handler.postDelayed(this::scheduleIfNecessary, 5);
   }
 
   /**