Federated authentication via ECP functional tests

Adds a first test for the federated authentication feature. It handles
first the authentication using the SAML2 ECP profile.

The tests cleanup have some issues, see related bug.

Related-Bug: 1642692
Change-Id: I3b393a695c6d9f846efdaf302c1beea34e6bd54b
10 files changed
tree: 70807168ef5c5d60c5e129846127c288f7b68430
  1. keystone_tempest_plugin/