Add missing tests for iscsi_* methods
Add missing tests for iscsi_* methods

There was no tests in test_db_api for iscsi_*
methods.

Bug 1187367 found.

blueprint db-api-tests

Change-Id: Ia554e6030307a0c4f0510ab74fe0881ee160f743

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