zebra: advertise evpn route upon l3vni svi mac chg

zebra: advertise evpn route upon l3vni svi mac chg

L3VNI keeps reference to svi interface (ifp).

When a netlink change received there is no flag
that mac has changed. Currently simply overwrite
interface's (ifp) hw_addr (MAC) field.

For originating EVPN type-2 and type-5 routes due to VNI
MAC change, comparison is required to check existing MAC
vs. netlink change MAC field.

Ticket:CM-23850
Reviewed By:CCR-8283
Testing Done:

Validate EVPN type-5 routes originated upon changing MAC address
of L3VNI's SVI inteface via ip link set cmd.

checked show bgp l2vpn evpn route and Rmac field contains new
MAC address.

Signed-off-by: Chirag Shah <chirag@cumulusnetworks.com>