Fix for ATR-30913: added a callback to outputThread for each noMoreEvent.

This should fix the timeouts at stop observed in ATLAS during M1. See https://its.cern.ch/jira/browse/ATR-30913 for more details.

HLT/Trigger/TrigControl/TrigServices/src/HltEventLoopMgr.cxx

@@ -1372,6 +1372,7 @@ StatusCode HltEventLoopMgr::startNextEvent()
     ++m_freeSlots;
     if (!m_loopStatus.loopEnded && m_inputThread!=nullptr) {
       m_inputThread->cond().notify_all();
+      m_outputThread->cond().notify_all();
     }
     return StatusCode::SUCCESS;
   }