fix(provider/openstack): Use directUrl property for image location

It's a workaround for issue in Openstack4j library, locations cannot be
used without fix ContainX/openstack4j#1096

Spinnaker issue: spinnaker/spinnaker#3018

clouddriver-openstack/src/main/groovy/com/netflix/spinnaker/clouddriver/openstack/client/OpenstackImageV2Provider.groovy

@@ -32,7 +32,7 @@ class OpenstackImageV2Provider implements OpenstackImageProvider, OpenstackReque
       .id(image.id)
       .status(image.status?.value())
       .size(image.size)
-      .location(image.locations?.get(0)?.toString())
+      .location(image.directUrl)
       .createdAt(image.createdAt?.time)
       .updatedAt(image.updatedAt?.time)
       .properties(properties)