Remove unused variable in os-extend api
Remove unused variable in os-extend api

Temp variable _val in _extend method is not being used, so remove this
'_val' variable.

Change-Id: I4a3f5e28d1882698a3efd116044c4fddff86c474
Closes-Bug: #1267423

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