Support the installation of Replica KDCs

[lhoss]

Is your feature request related to a problem? Please describe.
I want to have mit-kdc running, in the case of a failure of the (primary) KDC master node.
This Use-case is covered by mit-kdc by using Replica KDCs.
From the official Doc: https://web.mit.edu/kerberos/krb5-devel/doc/admin/install_kdc.html#install-the-replica-kdcs

Describe the solution you'd like
Thus I want to have a deployment that supports the installation of Replica/Slave kdc nodes,
which could be provided through a list variable or an inventory group.
Initial code used by another fork (in commits 2 + 3): bennojoy/kerberos_server@master...booz-allen-hamilton:develop

Describe alternatives you've considered
I checked for other mit-kdc/kerberos roles, but I found none with that feature (and most were of inferior quality)

Roles I found and checked:

• quite decent (derived also from bennojoy, but not as a fork): https://github.com/AlberTajuelo/ansible-kerberos-server
• the original, way too outdated (old ansible syntax etc): https://galaxy.ansible.com/bennojoy/kerberos_server

Additional context
I found your repo in the github forks from the original (outdated!) bennojoy role, and it made a good impression to me quality-wise.
Now also found it on galaxy (and gave it a 5/5 score, upfront 👍 ): https://galaxy.ansible.com/horizonnet/kerberos_server