Reduce test and optional requirements to global requirements

Currently SQLAlchemy 0.9 and pyMySQL are not available on OpenStack
PyPi mirror, which means we can't run tests with them at gating.

Related-bug: 1280008
Change-Id: I23a8b7ab31d7fb9f6ae7454c242a2ba854484cea
Remove locale overrides form tox template

Change Iad912181bc00827908887d45a448f559d5083194 removed them from
tox.ini, so we should remove them from tox-tmpl.ini, too, so that
they don't reappear when tox.ini gets regenerated by toxgen.

Change-Id: Ib3544a95cf1e17230fea9b5699a9b84adb09d973