Update python-swiftclient to >=2.2.0 for Heat

The generate_temp_url function in version 2.2.0 of python-swiftclient is
needed for the SwiftSignal resource in Heat:
https://review.openstack.org/#/c/96947/

Change-Id: I393a08fef09377ca2e41e5961849d6dd44514f8a
Merge "Update python-swiftclient to >=2.2.0 for Heat"