Fixing queue url generation, fixing get_build_dict and updating tests

Some fixes:

-The queue url generation was broken, the "api/python" part was duplicated. This change includes the url generation with urlparse.urljoin() to avoid mispelling errors.
-If there is a build running, you couldn't get it because get_build_dict only searched in _data['builds'] and ignored _data['lastBuild']. Because of that, the method get_last_build, get_last_build_or_none and is_running were broken when a build was running.
-Tests updated to work with the new changes and also changing the test_job.py fake data to have a running build so the fixed error is covered.