Using a proc in type title patterns causes an error when generating
puppet types for environment isolation. For example, running `puppet
generate types` on a puppet master produces the following error:
```
Error:
/etc/puppetlabs/code/environments/production/modules/keystone/lib/puppet/type/keystone_user_role.rb:
title patterns that use procs are not supported.
```
This commit changes the `project_domain` parameter to always default to
`DEFAULT_DOMAIN` even when using a `<user>::<user_domain>@::<domain>` or
`<user>@::<domain>` title pattern. The only place I could find that
utilized `project_domain` being unset was determining `keystone_domain`
autorequires. The logic was updated to reflect that `project_domain` is
either set or should use the default unless `domain` is set.
Change-Id: Icd29c5aa89ae442ca69cad0411188162462bf6ff
e17812f1ce