async-wrap: remove before/after calls in init

It doesn't make sense to call before/after callbacks in init to the
parent because they'll be made anyway from MakeCallback. If information
does need to be propagated then it should be done automatically. Will
deal with this if the issue arrises in the future.

PR-URL: https://github.com/iojs/io.js/pull/1614


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>