Add api-int DNS record to coredns

[cybertron]

Add a static mdns record that points to the API VIP. This is to
support the new required DNS record from OpenShift.

[cybertron]

This is going to require changes in mdns-publisher as well. It also doesn't address the bootstrap node, which doesn't currently run mdns-publisher.

[derekhiggins]

Build SUCCESS, see build http://10.8.144.11:8080/job/dev-tools/629/

[markmc]

Please add a reference in the commit to the background context on the openshift change - e.g. openshift/installer#1633 is a good reference

[cybertron]

I updated my local commit message, so references should be there when I'm ready to drop the WIP from this. We need openshift/mdns-publisher#7 before this will be effective though.

[cybertron]

This version no longer has a dependency on mdns-publisher.

[derekhiggins]

Build SUCCESS, see build http://10.8.144.11:8080/job/dev-tools/667/

[hardys]

Hmm does this depend on other commits? Since @cybertron mentioned it no longer depends on mdns-publisher I tried it locally and the masters can't resolve the api-int address to collect the ignition config.

[derekhiggins]

Build SUCCESS, see build http://10.8.144.11:8080/job/dev-tools/675/

[hardys]

Ignore my previous comment, I accidentally tested on a branch with #560 applied and CI confirms this as working so lgtm