Currently, the deployment of tempest will fail if heat does not exist
in the environment. This commit updates
os_tempest/tasks/tempest_resources.yml so that users are only added
to heat_stack_owner role if tempest_service_available_heat is set to
True.
Change-Id: Ib3f6a11de60be86c1b2581d3c8da615d66ebae5b