Bump os-testr to 0.7.0
Bump os-testr to 0.7.0

 * rise version according to https://github.com/openstack/requirements/blob/master/upper-constraints.txt#L190

Change-Id: I30c5a37a068998d7bbec5170cc9c75bdc4781131

openstack/rpm-packaging,openstack/rpm-packaging