test: dynamic port in parallel regress tests

[sebastianplesciuc]

Removed common.PORT from test-regress-GH-5051 and
test-regress-GH-5727 in order to eliminate the possibility
of port collision.

Refs: #12376

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

[Trott]

${0} can just be 0

[Trott]

For test/parallel/test-regress-GH-5051.js, do we actually need to do all this? It creates a request but it never actually runs the request, does it? (Honest question; I'm actually not sure.) If it never tries to connect to a port or anything, then we can just hard-code it to 80 or 8080 or whatever and not do all the net stuff.

[Trott]

I'm pretty sure the 5051 test never actually runs a network request, so we can dispense with net and hardcode any port we like. (I propose 8080.) If you believe differently, by all means, fill me in.

[sebastianplesciuc]

@Trott You're right. I changed it to 8080 and fixed the ${0} issue. Thank you!

[Trott]

LGTM if CI is green. Might want to consider adding a comment where 8080 is being hardcoded explaining that there's no network connection that actually happens; it's a request that gets created but never used. But I'm fine with it as-is too.

[sebastianplesciuc]

@Trott Added comment :)

[Trott]

CI: https://ci.nodejs.org/job/node-test-pull-request/7696/

[addaleax]

Landed in e927809, thanks for the PR!