Image services need keystoneclient not keystone

The service recipes have been pulling in the entire
python-keystone package, which is the entire Keystone
set of services. This hasn't been necessary since
some time after Grizzly, when the tokenauth middleware
was moved to the client.

Change-Id: Ice189991bab0b69eb4df42e968d31d93cb623bb8
Related-Bug: #1305318