etc: replace NullHandler by Python one
etc: replace NullHandler by Python one

We don't need to specify the NullHandler that was provided by Oslo
anymore, as Python 2.7 has this one. Let's use it directly.

Change-Id: I6948d1cd5a556779c1b1fd0a4161689e3a944b45

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