1) Revert "Remove tests for master branch", commit
d149f30a4b.
2) Use test-requirements.txt from stable/queens to select the
stable/queens branches of python-opflex-agent and
python-group-based-policy-client, and the noiro-lite branch of
acitoolkit.
3) Use pushd/popd in tox_install.sh to restore initial CWD after
switching requirements branch.
Change-Id: I39895732aac0bdfaee95274cbcb262d6744faeb1
9e2cb1fc9d