Build UKTradeTariff MySQL db when on preview
Build UKTradeTariff MySQL db when on preview

As part of the move away from RDS, use the new MySQL instance that
we have built for UKTradeTariff.

This builds out the database, sets up the slave, and the replication
box.

Also clean up the related comment to have capitalisation and use a
full stop.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet