Unpinning upper bound on python-*clients

If any of the projects specify a capped client, it has the
potential for preventing that client from being tested in the
gate. To fix this, maximum versions are uncapped for all
openstack client code in all openstack projects.

python-neutronclient is treated as an exception for now.

Fixes: bug #1200214

Change-Id: I64c68db0632b6547a6340c952bdb9cafe11ea1d9