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.

/cc @jasnell

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

test