Tempest currently has two different internal methods for providing
authentication to tests: dynamic credentials and pre-provisioned credentials.
Depending on which one is in use the configuration of Tempest is slightly
different.
We should provide a support for both of them.
https: //docs.openstack.org/tempest/latest/configuration.html#credential-provider-mechanisms
Change-Id: I26d69caa3f96a530bc0a4a21365404b1a84e489a