Registry fixture does not handle concurrent uses

[Ryan Rossiter]

The VersionedObjectRegistryFixture cannot handle races with things that are registering vs. things that need the original registry intact (i.e. object version hash checking).

What the registry fixture needs to do is return a new version of the registry, so the tests can mangle it all they want without changing the underlying object classes on the original registry.

[Ryan Rossiter (rlrossit)]

Patch for the fix: https://review.openstack.org/#/c/282090/

[Ihar Hrachyshka (ihar-hrachyshka)]

I am not sure the bug is valid. Neutron successfully uses the registry fixture in its tree for multiple tests. I think we identified lately that it was the way neutron tried to use the fixture that was wrong, not the fixture itself.