There's a case to be made that there should just be one global
mapping for all test instances.  That would be useful in at least
some ways.  However, it might complicate making local tests of
the automated update system.

Assuming we're not ready to create a global version mapping service,
a cheaper alternative would be to have push to prod test script copy
relevant mappings from the prod database into the test instance.
That can be done in about a dozen lines or so of bash; the python
equivalent isn't notably harder.

@charlene - can you take a look?

I don't quite understand 'have push to prod test script copy
relevant mappings from the prod database into the test instance'. DO you mean that always copying prod database into push database?

Will teach test push to sync the stable_version db with cautotest.