fix data race on vptr SignalListener::run

Author: CheSema

src/Daemon/BaseDaemon.h

@@ -125,7 +125,7 @@ class BaseDaemon : public Poco::Util::ServerApplication, public Loggers
     virtual void logRevision() const;
 
     /// thread safe
-    virtual void handleSignal(int signal_id);
+    void handleSignal(int signal_id);
 
     /// initialize termination process and signal handlers
     virtual void initializeTerminationAndSignalProcessing();