we have used domain scope arguments --project-domain, --user-domain
and --group-domain in identity commands, for example, role add v3,
to prevent resources conflict from same resource name existence.
To keep with the style of identity commands, it's better to rename
--domain to --project-domain.
Closes-Bug: #1468988
Change-Id: Ic6ccb895cf9be4a3d5f0001525e3b80cd340da8b