Add Stoppable prepare and start interfaces

src/ripple_core/functional/JobQueue.cpp

@@ -648,7 +648,7 @@ private:
 
     //--------------------------------------------------------------------------
 
-    void onStop ()
+    void onStop (Journal)
     {
         // VFALCO NOTE I wanted to remove all the jobs that are skippable
         //             but then the Workers count of tasks to process
@@ -700,7 +700,7 @@ private:
         */
     }
 
-    void onChildrenStopped ()
+    void onChildrenStopped (Journal)
     {
         ScopedLock lock (m_mutex);