tox: addex SSL proxy variables to passenv
tox: addex SSL proxy variables to passenv

Fix tox execution failures from system that are using SSL based
http proxies.

Related: https://github.com/tox-dev/tox/issues/1437
Signed-off-by: Sorin Sbarnea <8938dff14221394d430a023580a32caf3bfb26a9@redhat.com>

willthames/ansible-lint