vm-hosts: Enable multicast querier on bridge

Having this option enabled dramatically improves the reliability of
collectd multicast traffic from physical machines and VMs on a separate
VM host from the receiving machine.

group_vars/vm-hosts.yml

@@ -72,6 +72,8 @@ vmhost_netdevs:
     Description: pyrocufflink.blue VM network bridge
     Name: br0
     Kind: bridge
+  Bridge:
+    MulticastQuerier: 'yes'
 - name: 60-mgmt
   NetDev:
     Description: Management VM network bridge