setup_mcrouter.sh: Use local route as wildcard fallback

In local dev we'll only ever have a single cache pool with all
keys routed to it. Set the wildcard fallback so that all keys are
routed even if the mcrouter config isn't fully up to date.

install/setup_mcrouter.sh

@@ -82,7 +82,8 @@ if [ ! -f /etc/mcrouter/global.conf ]; then
       },
     },
     "wildcard": {
-      "type": "NullRoute",
+      "type": "PoolRoute",
+      "pool": "local",
     },
   },
 }