Updated openstack/openstack
Project: openstack/python-novaclient  06b28391e7ba6a2e1852ed3c5f246f3043f27e85
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Updates tox.ini to use new features

tox 1.6 allows us to skip the sdist step, which
is slow. This does that.
It also allows us to override the install line.
In this case, it's important as it allows us to
stop getting pre-release software we were not
asking for.

Original patch by Monty Taylor, talked about here:
http://lists.openstack.org/pipermail/openstack-dev/2013-September/015495.html

Change-Id: Iddf85d33b57f256d72756b516c23492e9600bedc