[BUGFIX] TestingToken must not rely on a session (Revision 1)

This changes the ``TestingToken`` to implement the
``SessionLessTokenInterface`` so that it doesn't rely on a session
to be started whenever it is authenticated.

This is required in order to make use of the token for CLI based
tests (e.g. from behat).
The change also removes the TestingProviderTest that were actually
outdated and only worked by accident.

Change-Id: Id5b8a64b07214dd562eb12b4c06a770ca1fae266
Releases: master, 2.2, 2.1
Revision-Id: dbe33b5e6d7c896bcf9209c4a273a40ddac5ed1b