Revert "for efficiency, run this method asynchronously"

This reverts commit 836e52e6.

@Asynchronous does deliver method calls in order, but the receiver
might end up executing multiple calls in parallel, so it doesn't really
guarantee the in-order execution.

That makes @Asynchronous somewhat useless, so I need to fix that in
remoting. But until I do so, it's safer to back out this change.