migrations: adds necessary migrations for settings.network

[etungsten]

Issue number:
N/A

Description of changes:

This adds the migration related to #1204 and #1231.

Author: Erikson Tung <etung@amazon.com>
Date:   Tue Jan 5 17:45:43 2021 -0800

    migrations: adds necessary migrations for `settings.network`
    
    Adds new migrations for migrating new settings and affected service
    settings. We also added new service settings for docker and
    host-containerd to incorporate restart commands for those services.

Testing done:

Built a custom TUF repository with a v1.0.5 aws-k8s-1.18 image.
Launched a v1.0.4 aws-k8s-1.18 host with a custom root.json and upgraded it to v1.0.5.
The instance came up fine and is able to run pods. Checked the settings and they got migrated as expected.
Rolled back the instance to v1.0.4, the host came back fine and is able to run pods. Backwards migration run successfully, all settings expected to be migrated got migrated.

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[tjkirch]

This looks fine, but won't we also need migrations to change the configuration-files lists for containerd, host-containerd, docker, and kubernetes to add proxy-env? I think you can do it with ReplaceListMigration, similar to the sysctl-subcommand migration.

[edit] I missed #1231 - also need to remove the restart commands for containerd and kubernetes, and the whole services.docker and services.host-containerd trees, I think.

Would you please test on an instance with a real repo? It's easier to do now with pubsys.

[etungsten]

New migrations to address #1258 (review) are pending changes in #1262 to be merged.

[etungsten]

Push above adds two new migrations for migrating the new restart-commands and configuration-file settings.

Updated PR description with new testing.

[zmrow]

🦺

[etungsten]

Push above changes the name of the migrations to address #1258 (comment)