During the review of I7e01f95d7173d9217f76e838b3ea71555151ef56
we made the decision to also add the migration uuid to the server
migrations GET responses to be consistent with the os-migrations
change to add the uuid to the response. This change simply amends
the spec to mention that change as well.
Part of blueprint add-pagination-and-change-since-for-migration-list
Change-Id: Icdd598d34748240a3ed9dade561f8f34857adbc3