[#55989114] Fix requirement to provision twice.

Because there is a call to heira before the machine_role var is setup,
it will not include the correct role-[machine_role].yaml. This means the
box does not get correctly setup and requires a second run of puppet
before it is correctly setup.
Merge pull request #30 from alphagov/fix-mulitple-provision-bug

[#55989114] Fix requirement to provision twice.