Why I did it
Radvd.conf.j2 template creates two copies of the vlan interface when there are more than one ipv6 address assigned to a single vlan interface. Changed the format to add prefixes under the same vlan interface block.
How I did it
Modifies radvd.conf.j2 and added unit tests
How to verify it
Configure multiple ipv6 address to the same vlan, start radvd
Unit test will check if radvd.conf with multiple ipv6 addresses is formed correctly
