This adds a role and related testing to manage our Kerberos KDC
servers, intended to replace the puppet modules currently performing
this task.
This role automates realm creation, initial setup, key material
distribution and replica host configuration. None of this is intended
to run on the production servers which are already setup with an
active database, and the role should be effectively idempotent in
production.
Note that this does not yet switch the production servers into the new
groups; this can be done in a separate step under controlled
conditions and with related upgrades of the host OS to Focal.
Change-Id: I60b40897486b29beafc76025790c501b5055313d
