test: fix flaky child-process-fork-regr-gh-2847

Windows would die with ECONNRESET most times when running
this particular test. This commit makes handling these errors
more tolerable.

PR-URL: https://github.com/nodejs/node/pull/4442


Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>