Adding mcast app to the required in ONOS_APPS

Change-Id: I3eb9e9b4d28ae2668ad7160cd427848bc3d26724
diff --git a/trellis/README.md b/trellis/README.md
index 6dd70c4..e173418 100644
--- a/trellis/README.md
+++ b/trellis/README.md
@@ -51,7 +51,7 @@
 Learn about how to setup ONOS at: https://wiki.onosproject.org/.
 After installation, the following ONOS apps need to be activated.
 
-`export ONOS_APPS=drivers,openflow,segmentrouting,fpm,dhcprelay,netcfghostprovider,routeradvertisement`
+`export ONOS_APPS=drivers,openflow,segmentrouting,fpm,dhcprelay,netcfghostprovider,routeradvertisement,mcast`
 
 ## ONOS - Network Config
 `onos-netcfg <onos-ip> routing/trellis/trellis.json`