test: fix sequential/test-async-wrap-getasyncid

Previously, this test would contain a DNS query that timed out
after 60 seconds, thus occupying one of the parallel test slots
for that period.

Fix that by creating a new channel for that request, and cancelling
it immediately.

PR-URL: https://github.com/nodejs/node/pull/15319


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>