tox: Remove redundant environment variables
TOX_ENV_NAME and VIRTUAL_ENV are both set by tox by default.
cf. https://github.com/tox-dev/tox/commit/be5373bab
Change-Id: Iee7c6fc0bd33865a8b8d8a8cf101cffd38515c2d Signed-off-by: Takashi Kajinami kajinamit@oss.nttdata.com