vrrp: VMAC code cleanup and extensions

Remastered VMAC code. Interface base_ifindex is set by default
to interface ifindex during netlink probe. VMAC interface
base_ifindex is now set during VMAC allocation uppon success
interface creation. Detect if virtual_router_id is declared
after use_mvac keyword is invoked. Add some more log while
setting up and removing VMAC interface.