Revert "temporarily disables run/reflection-sync-subtypes"

This reverts commit 04e2dbb29830d0e511cdfa8c132a9fad91d657ed,
by avoiding the ill-fated attempt to short-circuit the global
reflection lock.

I think we can do better performance wise, but lets at least
get something correct to start with.
Merge pull request #3143 from retronym/ticket/reflection-sync-restor

Revert "temporarily disables run/reflection-sync-subtypes"