Drain events before terminating log/thread managers.

Using the default scripts, the events from RemoteSerializer::LogStats()
were attempting to use the logging framework after logging/threading
had been terminated which never worked right and sometimes caused
crashes with "fatal error: cannot lock mutex".

Also made communication log baseline test pass more reliably.

src/main.cc

@@ -313,6 +313,8 @@ void terminate_bro()
 	if ( remote_serializer )
 		remote_serializer->LogStats();
 
+	mgr.Drain();
+
 	log_mgr->Terminate();
 	thread_mgr->Terminate();