Add unit tests to tempest auth file

Some unit tests to tempest/auth.py which implements request authentication for
keystone v2 and v3 in tempest.

Still missing some tests to base_url methods that were failing, and need to be
reworked.

Partially implements bp unit-tests

Change-Id: I367caf4d83a33ad1675c2069e8ac0c442246f322
4 files changed