Use Tempest 'all' tox env
Tempest recently moved tox default
to py3 including all-plugin env.
This will fail the py2 jobs which are using
all-plugin tox env. Because tox all-plugin
env var enable the sitepackages=True. Py2 jobs
install the tempest plugins on py2 and all-plugin
tox try to find the installed plugins on py3 which
cause no test to run and fail the job.
tox all-plugin has been deprecated since long and not
supposed to use for plugins who already in migrated to
separate repo in queens cycle.
Using tox 'all' env to fix the issue.