bgpd: evpn convey svi_ip to zebra post vni add

bgpd: evpn convey svi_ip to zebra post vni add

Problem:
With advertise_svi_ip knob enabled per vni.
Post vni flap, svi MAC-IP route are not originated.

Fix:
When a vni is flapped, upon re-add
send advetise_svi_ip knob to zebra.

Workaround:
re-configure advertise-svi-ip under l2vpn/evpn.

Ticket:CM-26001
Reviewed By:CCR-9118
Testing Done:

With advertise-svi-ip enabled under l2vpn/evpn
in bgp default instance.
Validated vni del/create post ifdown vxlan device
followed by ifup vxlan device.

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