events: preset `usingDomains` to false

The line setting this was removed in a previous commit. This
potentially breaks code in the wild using this property.

Refs: https://github.com/nodejs/node/pull/17403#issuecomment-367814130
PR-URL: https://github.com/nodejs/node/pull/18944


Reviewed-By: Vladimir de Turckheim <vlad2t@hotmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>