cinder example was missing a required arg

The example for the cinder quota-defaults command did
not indicate that you need to pass in a tenant ID.

I changed the example so that it includes the
tenant ID.

Change-Id: I7059a01a3b7f5df3717c10fd132f5f92eb596cc6
Closes-Bug: #1348016
Merge "cinder example was missing a required arg"