test: parallel/test-https-agent-unref-socket requires external network connection

[AdamMajer]

• Version: 16.3.0
• Platform:
• Subsystem: test

What steps will reproduce the bug?

Commit 4e33532 introduced a network fragile test which fails when there is no network available,

[ 1771s] not ok 1637 parallel/test-https-agent-unref-socket
[ 1771s]   ---
[ 1771s]   duration_ms: 1.399
[ 1771s]   severity: fail
[ 1771s]   exitcode: 1
[ 1771s]   stack: |-
[ 1771s]     node:events:371
[ 1771s]           throw er; // Unhandled 'error' event
[ 1771s]           ^
[ 1771s]     
[ 1771s]     Error: getaddrinfo EAI_AGAIN example.com
[ 1771s]         at GetAddrInfoReqWrap.onlookup [as oncomplete] (node:dns:69:26)
[ 1771s]     Emitted 'error' event on ClientRequest instance at:
[ 1771s]         at TLSSocket.socketErrorListener (node:_http_client:447:9)
[ 1771s]         at TLSSocket.emit (node:events:394:28)
[ 1771s]         at emitErrorNT (node:internal/streams/destroy:193:8)
[ 1771s]         at emitErrorCloseNT (node:internal/streams/destroy:158:3)
[ 1771s]         at processTicksAndRejections (node:internal/process/task_queues:83:21) {
[ 1771s]       errno: -3001,
[ 1771s]       code: 'EAI_AGAIN',
[ 1771s]       syscall: 'getaddrinfo',
[ 1771s]       hostname: 'example.com'
[ 1771s]     }
[ 1771s]   ...

[batrla]

This fix is missing on Node.js 14 branch, causing test failure if running make test on system w/o internet connection:

out/Release/node /some/path/nodejs14/build/amd64/te
st/parallel/test-https-agent-unref-socket.js
events.js:377
      throw er; // Unhandled 'error' event
      ^

Error: connect EHOSTUNREACH 93.184.216.34:443
    at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1148:16)
Emitted 'error' event on ClientRequest instance at:
    at TLSSocket.socketErrorListener (_http_client.js:475:9)
    at TLSSocket.emit (events.js:400:28)
    at emitErrorNT (internal/streams/destroy.js:106:8)
    at emitErrorCloseNT (internal/streams/destroy.js:74:3)
    at processTicksAndRejections (internal/process/task_queues.js:82:21) {
  errno: -148,
  code: 'EHOSTUNREACH',
  syscall: 'connect',
  address: '93.184.216.34',
  port: 443
}

How do I request backporting the fix to 14.x branch?