Add region support to openstack runner.

Hello.  I've added region support to the test-kitchen openstack runner.  On HP Cloud if the region is not specified the following error is returned:

/Users/tpot/.rvm/gems/ruby-1.9.3-p125@global/gems/fog-1.6.1/lib/fog/openstack.rb:140:in `authenticate_v2': Multiple regions available choose one of these 'az-3.region-a.geo-1,az-2.region-a.geo-1,az-1.region-a.geo-1' (Fog::OpenStack::Errors::NotFound)