Use --or-show for get_or_create_user/project/role function

Exploit the --or-show functionality of openstackclient,
rather than issuing two different commands at the shell level,
let the CLI handle things.

Change-Id: I1db239fd3473eb580def1c5fb28ce472a1363569
Merge "Use --or-show for get_or_create_user/project/role function"