Review EMCO APIs for IPv6 support

I reviewed the code for any usage of literal IPv4 addresses and added support for literal IPv6 addresses where needed. I was able to test most of this against two dual-stack K8s clusters, with the following exceptions:

• Istio doesn't appear to support dual-stack, but EMCO looks like it is operating correctly.
• Development is ongoing in Nodus to fully support IPv6, so I could not validate end-to-end ovnaction, sfc, and sfcclient services.

Signed-off-by: Todd Malsbary todd.malsbary@intel.com