zebra: check vni oper state in svi up notif

zebra: check vni oper state in svi up notif

When clagd is stopped on secondary device,
all vxlan interfaces (vnis) are kept in protodown state.
FRR treats protodown vxlan interfaces (vnis) as interface down
and sends vni delete to bgpd.

In the event of clagd down, SVIs are flapping as underlying
bridge is going through churn.
When FRR receives SVI up notification do not trigger event to bgpd
if vnis are operationaly down.

Ticket:#2600210 CM-22929
Reviewed By:CCR-11544
Testing Done:
Performed CLAG stop/start on secondary device, all vxlan devices
remained in protodown along with this validated the vnis are cleaned up
and added back in bgpd.

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