Before change I4244f7dd8fe74565180f73684678027067b4506e in Stein, when
a cold migration would reschedule to conductor it would not send the
RequestSpec, only the filter_properties. The filter_properties contain
a primitive version of the instance group information from the RequestSpec
for things like the group members, hosts and policies, but not the uuid.
When conductor is trying to reschedule the cold migration without a
RequestSpec, it builds a RequestSpec from the components it has, like the
filter_properties. This results in a RequestSpec with an instance_group
field set but with no uuid field in the RequestSpec.instance_group.
That RequestSpec gets persisted and then because of change
Ie70c77db753711e1449e99534d3b83669871943f, later attempts to load the
RequestSpec from the database will fail because of the missing
RequestSpec.instance_group.uuid.
The test added here recreates the pre-Stein scenario which could still
be a problem (on master) for any corrupted RequestSpecs for older
instances.
Change-Id: I05700c97f756edb7470be7273d5c9c3d76d63e29
Related-Bug: #1830747
c96c7c5e13