Move Custom Stack Provisioner pre step to be after facts initialisation

[cliffano]

Custom Stack Provisioner pre step is currently executed before any fact initialisation. It was initially expected to be an independent set of provisioning steps that wouldn't need any Facter fact.

However, when the Custom Stack Provisioner uses Puppet, it's useful to have those facts available, e.g. to identify whether the execution is for a particular component.

This pre-step needs to be moved to be after facts initialisation.