Use known protocol scheme in keystone tests

With the recent introduction of the identity_uri in keystoneclient,
there is a small backward incompatible change which means that weird
protocols like the ones we use during tests aren't support properly
anymore. The patch replaces "foottp" and "barttp" by "file" hopefully
keeping testing coverage the same.

Change-Id: Idb30ff3ee0ca50911e453899ad32e630f9b18724
Closes-Bug: #1309092
(cherry picked from commit e5b7606eaa94033256eb1aca5f6a6eed4f9e54a0)
(cherry picked from commit a1ec218d683e27434a5b085f1fbc7e3c13b60684)