Add --or-show option to user create

The --or-show option is added to create commands for the common case
of needing to ensure an object exists and getting its properties if
it does or creating a new one if it does not exist.

Note that if the object exists, any additional options that would
set values in a newly created object are ignored if the object
exists.

FakeResource needs the __name__ attribute to fall through utils.find_resource.

Prove the concept on v2 user create then propogate once we're happy with it...

Change-Id: I6268566514840c284e6a1d44b409a81d6699ef99
Merge "Add --or-show option to user create"