the reason is that I need the `usePoolDispatcher` Boolean, which is set from config, e.g. here https://github.com/akka/akka/pull/1776/files#diff-b4eba0e378a0bae81c9670c7ee78529fR72

At that point the user config is already merged with default config, so there is no way to see if the user has configured it.
I could remove pool-dispatcher from the default config, and use `hasPath`.

This reminds me that I forgot to add that usePoolDispatcher initialization from config in *all* pools.