Fix test novaclient.create
Fix test novaclient.create

Older novaclient doesn't have attribute discover_extensions.
So we need to consider it till novaclient version will bump one
day.

Change-Id: I644d18605e80791e1891981bf70ad52ec3dfe2c4

jasondunsmore/heat,dims/heat,srznew/heat,steveb/heat,openstack/heat,rh-s/heat,dragorosson/heat,steveb/heat,maestro-hybrid-cloud/heat,cryptickp/heat,gonzolino/heat,dims/heat,maestro-hybrid-cloud/heat,noironetworks/heat,rh-s/heat,cwolferh/heat-scratch,pratikmallya/heat,srznew/heat,cryptickp/heat,pratikmallya/heat,takeshineshiro/heat,gonzolino/heat,miguelgrinberg/heat,noironetworks/heat,cwolferh/heat-scratch,takeshineshiro/heat,dragorosson/heat,miguelgrinberg/heat,jasondunsmore/heat,openstack/heat