gluon-client-bridge: reenable multicast snooping for client zone

LEDE recently disabled multicast snooping by default:

https://git.lede-project.org/?p=project/netifd.git;a=commitdiff;h=52541140f8138e31958cdc3d7e42a4029fa6bbc9

Reenable it for Gluon as there have been no confirmed issues for
LEDE and no negative reports concerning Gluon v2016.2.x so far.

Closes #1025.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>

package/gluon-client-bridge/luasrc/lib/gluon/upgrade/300-gluon-client-bridge-network

@@ -34,6 +34,8 @@ uci:section('network', 'interface', 'client', {
 	auto = true,
 	ipv6 = false,
 	macaddr = sysconfig.primary_mac,
+	igmp_snooping = true,
+	multicast_querier = true,
 })
 
 uci:save('network')