Now that the nova code supports such a migration this patch removes the
check from the API that rejected the operation.
Note that in the spec [1] we agreed not to introduce new microversion
for this change but treat it as a bugfix. The current change also makes
it possible to accept the migration of these servers with _any_
microversion.
[1] https://specs.openstack.org/openstack/nova-specs/specs/train/approved/support-move-ops-with-qos-ports.html#rest-api-impact
Change-Id: I4bda569cc7c247e83219276282724c77e760ddcd
blueprint: support-move-ops-with-qos-ports