Add purge/recurse to the when provider is MariaDB.

[bschonec]

Summary

When the provider is MariaDB, the $includedir directory is not purged of extraneous files.

Additional Context

There is special handling for the MariaDB provider (for reasons unknown). The purge property is not set.

Related Issues (if any)

1590

Checklist

• [ ] 🟢 Spec tests.
• [ ] 🟢 Acceptance tests.
• [ ] Manually verified. (For example puppet apply)

[bschonec]

I request that this also be back-ported to v14.0.0 for those of us (me) who are unable to run v15.x.x or newer.

[bschonec]

This is a pretty simple enhancement. Any chance someone could approve this?