[release-3.11] Restore graceful shutdown of DNS server

[Miciah]

Restore signal handling and graceful shutdown of DNS that had been added in commit c802e22 but was subsequently lost during rebase in commit 564ee03.

Graceful shutdown is necessary to ensure that when OpenShift's DNS server shuts down, we remove it from the dnsmasq configuration.

This commit fixes bug 1624448.

https://bugzilla.redhat.com/show_bug.cgi?id=1624448

This is a manual cherry-pick of #21009

[Miciah]

/retest

[Miciah]

/retest

Seen this error from docker login in test/end-to-end/core.sh a couple times now:

Error response from daemon: login attempt to http://172.30.1.1:5000/v2/ failed with status: 500 Internal Server Error

[Miciah]

Same docker login failure.

/retest

[Miciah]

/retest

[knobunc]

/retest

[ironcladlou]

/lgtm

[ironcladlou]

/retest

[Miciah]

I opened BZ#1630537 e2e flake: docker login to internal registry fails with "500 Internal Server Error" for the end-to-end test flake.

[knobunc]

/approve

[knobunc]

@smarterclayton Can I green box merge this? There seems to be some flake killing the tests and it must be in for QE tonight.

[pravisankar]

/lgtm

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ironcladlou, knobunc, Miciah, pravisankar

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:

• pkg/cmd/OWNERS [knobunc]

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]

@Miciah: The following test failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
ci/openshift-jenkins/end_to_end	4c6c0eb	link	/test end_to_end

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.