add error flow tests for volume detach
add error flow tests for volume detach

engine.resources.volume.VolumeAttachment lacks tests for some
exception flows

Fixes bug #1183239

Change-Id: I3d84fadb1ff60c622fbfbd634e003aaab382b405

cwolferh/heat-scratch,cryptickp/heat,NeCTAR-RC/heat,srznew/heat,redhat-openstack/heat,rickerc/heat_audit,dims/heat,pshchelo/heat,citrix-openstack-build/heat,rh-s/heat,maestro-hybrid-cloud/heat,openstack/heat,JioCloud/heat,miguelgrinberg/heat,steveb/heat,jasondunsmore/heat,takeshineshiro/heat,takeshineshiro/heat,dims/heat,redhat-openstack/heat,gonzolino/heat,miguelgrinberg/heat,varunarya10/heat,srznew/heat,noironetworks/heat,rh-s/heat,rdo-management/heat,jasondunsmore/heat,noironetworks/heat,cwolferh/heat-scratch,steveb/heat,dragorosson/heat,rdo-management/heat,maestro-hybrid-cloud/heat,pratikmallya/heat,JioCloud/heat,NeCTAR-RC/heat,pratikmallya/heat,gonzolino/heat,dragorosson/heat,rickerc/heat_audit,cryptickp/heat,pshchelo/heat,openstack/heat,ntt-sic/heat,varunarya10/heat,citrix-openstack-build/heat,ntt-sic/heat