event/TimeoutMonitor: reset "active" flag before invoking OnTimeout()

The IsActive() method returned true even if the timer was not active,
after it completed once.  This broke the state file timer, and the
state file was not saved periodically.

src/event/TimeoutMonitor.cxx

@@ -64,7 +64,9 @@ TimeoutMonitor::ScheduleSeconds(unsigned s)
 void
 TimeoutMonitor::Run()
 {
-#ifndef USE_EPOLL
+#ifdef USE_EPOLL
+	active = true;
+#else
 	Cancel();
 #endif