test: improve message in net-connect-local-error

test-net-connect-local-error can fail with messages that report
`AssertionError: undefined === 12346`. Unfortunately, this doesn't
provide sufficient information to identify what went wrong with the
test. Increase information provided.

PR-URL: https://github.com/nodejs/node/pull/11393


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>