Python 3: replace "im_self" by "__self__"
Python 3: replace "im_self" by "__self__"

The Python 3 removed the "im_self" attribute and only supports the
"__self__". This patch replaces "im_self" by "__self__" attribute.

Closes-Bug: #1282514
Change-Id: Ib017fff4b720a5dd7ee27fd01b36a531d9b6ca9c

Hybrid-Cloud/cinder,scottdangelo/RemoveVolumeMangerLocks,nexusriot/cinder,potsmaster/cinder,eharney/cinder,duhzecca/cinder,alex8866/cinder,nikesh-mahalka/cinder,abusse/cinder,julianwang/cinder,potsmaster/cinder,hguemar/cinder,NeCTAR-RC/cinder,nexusriot/cinder,JioCloud/cinder,tlakshman26/cinder-bug-fix-volume-conversion-full,blueboxgroup/cinder,rakeshmi/cinder,dims/cinder,takeshineshiro/cinder,julianwang/cinder,spring-week-topos/cinder-week,tlakshman26/cinder-new-branch,j-griffith/cinder,winndows/cinder,Accelerite/cinder,leilihh/cinder,openstack/cinder,CloudServer/cinder,takeshineshiro/cinder,eharney/cinder,github-borat/cinder,j-griffith/cinder,abusse/cinder,petrutlucian94/cinder,apporc/cinder,Datera/cinder,tlakshman26/cinder-bug-fix-volume-conversion-full,saeki-masaki/cinder,Accelerite/cinder,phenoxim/cinder,phenoxim/cinder,NetApp/cinder,mahak/cinder,tlakshman26/cinder-new-branch,Akrog/cinder,dims/cinder,rakeshmi/cinder,bswartz/cinder,Nexenta/cinder,sasukeh/cinder,Thingee/cinder,scality/cinder,cloudbase/cinder,apporc/cinder,Hybrid-Cloud/cinder,spring-week-topos/cinder-week,scottdangelo/RemoveVolumeMangerLocks,Datera/cinder,manojhirway/ExistingImagesOnNFS,nikesh-mahalka/cinder,tlakshman26/cinder-https-changes,redhat-openstack/cinder,blueboxgroup/cinder,tlakshman26/cinder-https-changes,Paul-Ezell/cinder-1,openstack/cinder,bswartz/cinder,JioCloud/cinder,duhzecca/cinder,ge0rgi/cinder,petrutlucian94/cinder,cloudbase/cinder,redhat-openstack/cinder,winndows/cinder,mahak/cinder,Thingee/cinder,sasukeh/cinder,manojhirway/ExistingImagesOnNFS,github-borat/cinder,leilihh/cinder,Akrog/cinder,Nexenta/cinder,saeki-masaki/cinder,scality/cinder,NeCTAR-RC/cinder,Thingee/cinder,hguemar/cinder,CloudServer/cinder,Paul-Ezell/cinder-1,NetApp/cinder,alex8866/cinder