domains: fix stack clearing after error handled

caeb6773 introduced a regression where
the domains stack would not be cleared after an error had been handled
by the top-level domain.

This change clears the domains stack regardless of the position of the
active domain in the stack.

PR: #9364
PR-URL: https://github.com/joyent/node/pull/9364


Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Julien Gilli <julien.gilli@joyent.com>