Cleanup tox.ini: Remove obsolete constraints
Cleanup tox.ini: Remove obsolete constraints

Remove old and unused constraints environments from tox.ini. Those
have never been used.

Note that the repo has in the past not used constraints in OpenStack
CI, this change keeps the status quo.

For more information about constraints see:
http://lists.openstack.org/pipermail/openstack-dev/2016-August/101474.html

Change-Id: Idb24ac27d5653b5f0c7a5f618b475c9e278fcc8a

openstack/ironic-staging-drivers,openstack/ironic-staging-drivers