Add support for passing optional ``requested_roles`` attribute
When passing ``requested_roles`` down the ``identity-service``
relation the Keystone charm will create the listed roles for you.
Useful for charm authors implementing charms with specific role
This adds back in the unit tests that were removed due to charm-tools
issue #192  where the ignore option was 'ignored' by charm-tools.
This meant that the unit tests could not be ignored, and they ended
up in the built charm which then failed.
This adds unit tests to the interface-keystone and provides ostestr
support, and a makefile to allow easy 'make lint' and 'make test'
commands. All tests are performed in tox environments. At present this