Update Automation To Facilitate More-Transparent Rebuilding

[Thomas H Jones II]

Problem Description:

Upon reprovisioning, all service-users that use SSH for push/pull operations receive spurious main-in-the-middle-attack errors.

Expected Behavior:

After a rebuild event, SSH-based git actions do not experience main-in-the-middle-attack warnings.

Actual Behavior:

After a rebuild event, SSH-based git actions experience (objectively spurious) main-in-the-middle-attack warnings.

Fix recommendation:

Ensure that, upon provisioning:

• A replacement-host checks for availability of prior host's SSH hostkeys, installing them if present
• If no prior hostkeys present, generate new ones and upload to a location that further replacement-hosts can pull from

[Thomas H Jones II]

Superseded by #27