[CONSOLED] Shouldn't call domain_create_ring() for a domU which is shutting down.

There is a race condition between domain_create_ring() and the removal
of the domU entry from xenstore. If the removal of the domU entry from xenstore
comes later than the first xs_gather() call in domain_create_ring(), it will go
on and bind the evtchn port to the dying domU, which will cause below error
message: (XEN) (file=event_channel.c, line=144) EVTCHNOP failure: domain 0, error -22, line 144

Signed-off-by: Max Zhen <max.zhen@sun.com>

tools/console/daemon/io.c

@@ -293,12 +293,14 @@ static bool watch_domain(struct domain *dom, bool watch)
 	bool success;
 
 	sprintf(domid_str, "dom%u", dom->domid);
-	if (watch)
+	if (watch) {
 		success = xs_watch(xs, dom->conspath, domid_str);
-	else
+		if (success)
+			domain_create_ring(dom);
+	} else {
 		success = xs_unwatch(xs, dom->conspath, domid_str);
-	if (success)
-		domain_create_ring(dom);
+	}
+
 	return success;
 }