Auth option prompting happens waaaay to early in the default
os-client-config flow, we need to defer it until adter the commands
have been parsed. This is why ClientManager.setup_auth() exists,
as it is not called until the first attempt to connect to a server
occurs. Commands that do not require authentication never hit this.
Also, required options were not being enforced. By doing this we handle
when no authentication info is present, we fail on missing auth-url rather
than attempt to prompt for a password (default auth is password).
Closes-Bug: 1619274
Change-Id: Ia4eae350e6904c9eb2c8507d9b3429fe52418726