db: log SQL worker shutdown state

src/db/Main.cpp

@@ -243,7 +243,9 @@ int main()
 
 	signal_timer_disable();
 
+	sys_log(0, "[SHUTDOWN] DB main loop finished, quitting SQL workers");
 	DBManager.Quit();
+	sys_log(0, "[SHUTDOWN] DB SQL workers stopped");
 	int iCount;
 
 	while (1)
@@ -260,6 +262,8 @@ int main()
 		sys_log(0, "WAITING_QUERY_COUNT %d", iCount);
 	}
 
+	sys_log(0, "[SHUTDOWN] DB process exiting cleanly");
+
 	log_destroy();
 	return 0;
 }