Assert that object is busy when we call unbusy

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@489 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_hash.c

@@ -128,6 +128,7 @@ HSH_Unbusy(struct object *o)
 	struct sess *sp;
 
 	assert(o != NULL);
+	assert(o->busy);
 	assert(o->refcnt > 0);
 	if (o->cacheable)
 		EXP_Insert(o);