workflowv2 is currently used type for Mistral. Old service type did not
really cause any issues, because if not specified, the default value
from --os-mistral-service-type is used, which is correct. Anyway, it is
worth fixing so that it doesn't cause confusion.
Change-Id: I2c4f33d38d9ce487bde6b99455bfdb42f4f21f85
Closes-Bug: 1688219