T4665: Keepalived: Fix interface names

When applying the same VRID for IPv4 and IPv6 with RFC3768
compatibility enabled, the IPv6 interfaces came back with the
wrong name. For example:

Name Interface VRID State Priority Last Transition

v4-10 eth1v10 10 MASTER 100 21s
v6-10 vrrpv10 10 MASTER 100 21s

Because of this, the IPv6 interface didn't show up in show int.

This change suffixes the interface with the IP version so
show int works again.

Name Interface VRID State Priority Last Transition

v4-10 eth1v10v4 10 MASTER 100 21s
v6-10 eth1v10v6 10 MASTER 100 21s

vyos@vyos:~$ show interfaces
Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
Interface IP Address S/L Description

[....]
eth1v10v4 192.168.10.60/24 u/u
eth1v10v6 2001:ffff::1/64 u/u
[....]