Add IPV6 radvd package to neutron-l3-agent
Add IPV6 radvd package to neutron-l3-agent

When a IPV6 subnet created in SLAAC mode, neutron-l3-agent fails if
radvd is not installed. 'radvd' daemon is required in generation of RA
messages by virtual routers.

Change-Id: I16e856bf4563ac1dba5b38b7ed7fdaa52e629ee4

mrangana/kolla,GalenMa/kolla,nihilifer/kolla,openstack/kolla,rahulunair/kolla,stackforge/kolla,stackforge/kolla,nihilifer/kolla,stackforge/kolla,mrangana/kolla,GalenMa/kolla,rahulunair/kolla,openstack/kolla