OpenStack: switch to CoreDNS

[tomassedovic]

This replaces the dnsmasq container used the OpenStack provider with
CoreDNS. OpenShift already uses CoreDNS so it doesn't make sense to
bring in a different DNS tech to the mix.

This also reads /etc/resolv.conf for upstream DNS rather than
hardcoding OpenStack's internal IP address. And it uses CNAMEs to
provide etcd IPs instead of generating a hosts file.

[flaper87]

Tested this locally and it does the job great!

/lgtm

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: flaper87, tomassedovic

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• data/data/openstack/OWNERS [flaper87,tomassedovic]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.

[openshift-ci-robot]

@tomassedovic: The following tests failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
ci/prow/e2e-openstack	a05975c	link	/test e2e-openstack
ci/prow/e2e-libvirt	a05975c	link	/test e2e-libvirt

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.