test: fix helper-debugger-repl.js

The test `debugger/test-debugger-repl-break-in-module` (and probably
others) was failing because the handshake message for debugging is no
longer `listening on port <port>` but is instead `listening on
<address>:<port>`.

This change makes the check less strict so as to hopefully future-proof
it at least a little bit against subsequent changes.

This test failure is not caught in CI because currently debugger tests
are not run in CI.

PR-URL: https://github.com/nodejs/node/pull/9486


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Minwoo Jung <jmwsoft@gmail.com>
Reviewed-By: Prince John Wesley <princejohnwesley@gmail.com>