Support for configuring local dummy interface addresses for service frontends

[SpComb]

Each clusterf-ipvs machine needs to have the ServiceFrontend address configured as a local address for packets to be processed by IPVS. For Gateway machines acting as the externally facing frontend, these must be routed within the external network, and configuring any macvla/ipvlan/VRRP/OSPF/etc mechanisms is outside the scope of clusterf.

However, for machines acting as clusterf Route.Gateway targets within the internal network, the network routing of ServiceFrontend network addresses is handled by clusterf. clusterf-ipvs could handle the configuration of a Linux dummy interface with the various frontend network addresses used for IPVS services.