zuul: Use all rather than all-plugin for tox_envlist

Since 'all-plugin' is deprecated in Tempest, this is to
switch to 'all' instead in .zuul.yaml; for more info,
see: https://github.com/openstack/tempest/blob/9b4c50cf634cbea6e6a7353fff14c2f0a7ab1aa2/tox.ini#L64

Depends-On: Ib3264f54075216471720483c8dd816887c1f413c
Change-Id: I440b6cff2b5378e18304017589e3e7cf4748c28c
2 files changed