Fix bug introduced with 99edb6c4 (mr !420)

https://coverity.cern.ch/reports.htm#v13572/p10041/fileInstanceId=763879735&defectInstanceId=396360581&mergedDefectId=98201

GaudiHive/src/IOBoundAlgSchedulerSvc.h

@@ -46,7 +46,7 @@ private:
   StatusCode deactivate();
 
   /// Flag to track if the scheduler is active or not
-  bool m_isActive;
+  bool m_isActive = false;
 
   /// The thread in which the activate function runs
   std::thread m_thread;