Fix tox -e py34
Fix tox -e py34

Add a py34 test environment to tox.ini running a subset of tests which
pass on Python 3.4. With this change, the py34 check job should pass and
so it will become possible to make the job voting to avoid further
Python 3 regressions.

Blueprint cinder-python3
Change-Id: If8a8bafe0ff7e8d27baa3467f1790c3cb776457e

nexusriot/cinder,phenoxim/cinder,scottdangelo/RemoveVolumeMangerLocks,CloudServer/cinder,openstack/cinder,scality/cinder,Paul-Ezell/cinder-1,CloudServer/cinder,manojhirway/ExistingImagesOnNFS,apporc/cinder,JioCloud/cinder,JioCloud/cinder,takeshineshiro/cinder,duhzecca/cinder,sasukeh/cinder,Hybrid-Cloud/cinder,potsmaster/cinder,Nexenta/cinder,mahak/cinder,ge0rgi/cinder,eharney/cinder,Hybrid-Cloud/cinder,Paul-Ezell/cinder-1,dims/cinder,potsmaster/cinder,cloudbase/cinder,winndows/cinder,tlakshman26/cinder-new-branch,Nexenta/cinder,tlakshman26/cinder-bug-fix-volume-conversion-full,winndows/cinder,mahak/cinder,j-griffith/cinder,takeshineshiro/cinder,sasukeh/cinder,dims/cinder,tlakshman26/cinder-https-changes,tlakshman26/cinder-https-changes,Datera/cinder,phenoxim/cinder,petrutlucian94/cinder,NetApp/cinder,scottdangelo/RemoveVolumeMangerLocks,tlakshman26/cinder-bug-fix-volume-conversion-full,scality/cinder,Datera/cinder,j-griffith/cinder,nikesh-mahalka/cinder,leilihh/cinder,nexusriot/cinder,eharney/cinder,bswartz/cinder,tlakshman26/cinder-new-branch,openstack/cinder,nikesh-mahalka/cinder,duhzecca/cinder,petrutlucian94/cinder,NetApp/cinder,manojhirway/ExistingImagesOnNFS,apporc/cinder,bswartz/cinder,cloudbase/cinder,leilihh/cinder