Fix typo in image_utils tempfile handling
Fix typo in image_utils tempfile handling

Commit cbcd340 changed from NamedTemporaryFile to mkstemp, but
mkstemp returns a file descripter, not a file object. We therefore
need to close the fd using os.close(). This was tested using
devstack.

Change-Id: I808fa470a141e249fe30ee762ee94f47ecfd3f63

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