labstore: Rewrite of replica-addusers.pl
- Switch it to opt-in per project rather than turned on by default for all projects. That caused a deluge of unnecessary and unused mysql accounts, and also presumed that all projects got NFS by default (which is not the case).
- Opt-in only tools by default.
- Keeps state only in the replica.my.cnf files themselves - no state kept elsewhere (other than in the mysql dbs themselves, ofc)
- Add support for user accoutns, not just service groups
- Figure out what to do if the replica.my.cnf file is missing but the user / grant already exists.