Refstack does not work with cryptography 37.0.0. In debugging how this
passes testing I noticed that Refstack's tox.ini uses openstack
constraints. Arguably it shouldn't do this as it isn't part of
coinstalled opensdtack services, but since this is how they test things
we should mimic it in our deployment.
Update the Dockerfile to copy in the upper-contraints file to the
/tmp/src dir which the assemble script should honor.
Change-Id: I4603702982e5c03b4a1d110363787b1f04887a29
b8bd982daf