Comment 9 for bug 1824299

@zzzeek so I reverted https://review.opendev.org/659511 and applied your above patch adding mutex into SQLAlchemy: in 1 out of 3 neutron server restarts I can still see "Class 'neutron.db.models.flavor.FlavorServiceProfileBinding' is not mapped" errors.
With just https://review.opendev.org/659511 - I did 5 restarts and no errors seen.
I understand https://review.opendev.org/659511 is not the right fix, but maybe it can help debug the race more. Thanks