don't advertise interface static routes and allowed address pair routes for standby

[Nischal Sheth]

Consider a VMI which has an instance IP which has AddressMode set to
active-standby. If the VMI has interface static routes configured on it
or allowed-address pairs, the agent always advertises corresponding IP
routes. The local-preference of these routes is determined based on
data plane liveness of these adresses.

This behavior causes issues when there are VMIs with different instance
IPs that are configured with the same interface static routes. Expected
behavior is that we see ECMP routes for the interface static routes or
allowed-address pair. However, this doesn't work consistently because
we seem to be comparing local-preference across the routes coming
from two different instance IPs.

Suggested fix is to not advertise routes for interface static routes and
allowed-address pairs when associated instance IP is in standby state.