use renamed mariadb services

This patch updates all the json files that reference the mariadb service
variables to ues the new names.

Labelling things foo-master crept into this repository from the
kubernetes guestbook example (which has redis-master and redis-slaves).
We're not running clustered software at the moment so these labels are
unnecessary.

Change-Id: I229d04c89aa13cb6cc2e1c33a0a7b21e1c6e9caa