catalog/from-k8s: adds support for ClusterIP Service

[jipperinbham]

addresses #4

In order to get the correct port, it has to loop through the endpoint ports while looping through the subsets. Also, in order to locate the correct "main" port, I moved the main variable outside the if ports condition to be referenced in the switch.

I believe this covers all the cases for ClusterIP services:

• 1 port w/ no name
• multiple ports (take first port defined in the service)
• multiple ports with annotated override

[jipperinbham]

I think this will also address #8 as the current release will use the NodePort for the Service port which doesn't work.

[leosunmo]

This would be immensely useful for me, I hope it doesn't fall through the cracks!

[darnould]

Can confirm that this made the from-k8s catalog sync functional for my use-case with ClusterIP services.

Well done @jipperinbham and thank you for your efforts. Very keen to see this merged/resolved in a release, HashiCorp! cc/ @mitchellh

[adilyse]

Huge thanks to @jipperinbham for doing the work to support ClusterIP services! A version of this has now been merged with the addition of an option to turn off ClusterIp syncing if anyone should so desire.