test: expand test-https-keep-alive-large-write

Check that `serverConnectionHandle.writeQueueSize === 0`
after a large write finished.

PR-URL: https://github.com/nodejs/node/pull/17564


Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: James M Snell <jasnell@gmail.com>