UDN: Access to services from the default network doesn't work in shared gateway mode with L3 topology in non-IC

[kyrtapz]

What is this issue about?

#4567 adds support for specific default services to be reachable from a UDN network. In Layer3 UDNs with shared gateway mode it adds routes to the cluster router which is not going to work in non-IC deployments. A potential solution is to use logical router policies, this is not preferable for IC deployments since it introduces more complexity to the already existing LRPs.