Add custom get_temp_url to RackspaceSwiftClient

Rackspace Cloud Files uses a non-OpenStack account identifier in the
URL, so the Rackspace Swift client needs its own get_temp_url method.

Change-Id: Ic90c26fca0200f1fba74d50b6aa8a75f8bcd7ef6
Closes-bug: #1378979
Merge "Add custom get_temp_url to RackspaceSwiftClient"