Make Instance.save() update numa_topology

This is needed so that we can actually update the given topology with
the updated data after a successful claim.

Deleting it will also be needed when we actually make the resize work
properly for instances with NUMA topology, so we add it here as well.

We do not expose the new InstanceNUMATopology methods as @remotable to
avoid having to bump the object version thus making this an easier
backport target. This is OK since they are only called from
Instance.save() which is @remotable, and can be trivially made remotable
should this be needed later (causing a version bump that need not be
backported).

Partial-bug: #1386236
(cherry picked from commit a59e1a9c7e54efaadc39d366772972463855dfc7)

Conflicts:
	nova/tests/unit/objects/test_instance.py

Change-Id: I64ff2d00ca20bd065bb17ebaa9c40b64b8cbb817
Merge "Make Instance.save() update numa_topology" into stable/juno