test: fixup test-http-hostname-typechecking

This test would currently create HTTP requests to localhost:80
and would time out on machines that actually had an server listening
there.

To address that, `end()` the requests that are generated.

PR-URL: https://github.com/nodejs/node/pull/12627
Ref: https://github.com/nodejs/node/pull/12494


Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>