test: fix test-debugger-pid

The current format that prints the process PID before the actual
message.

Adapt the test so it also passes on Windows, that emits a different
message from the rest of platforms.

Move the test to parallel.

PR-URL: https://github.com/nodejs/node/pull/6584


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rich Trott <rtrott@gmail.com>