During cloud discovery resource creation, the domain_name and
user_domain_name information used to be hard coded to 'Default' which
might not be the case for all credentials, admin or non-admin.
This patch adds support for domain_name, project_domain_name and
user_domain_name information by defaulting all of them to 'Default'
however in the case they are available in the cloud credentials, using
them during python-tempestconf runtime as well as rendering them
correctly in the final tempest configuration.
Story: 2010811
Task: 48330
Change-Id: I4355837f4d8d514524039df6f3989dbd69f2c700
58e32bbe5a