Notify parent processes when server is ready to listen.

Avoid race conditions in server startup (both for parsoid and for the
mockAPI) by using the node child_process.fork() message-passing channel
to have the child process asynchronously notify the parent process
when it has completed startup and is successfully listening on the
specified port.

Change-Id: I2221914f956e0e2ae44dd13132814f498d6df74e
Add normalized filename for LoremIpsum.djvu to mockAPI.js

* Fixes incorrect API response of missing file for that parser test
* Updated the relevant parser test with new wt2html output.
* That test fails wt2wt mode because serializer doesn't yet
  handle the page parameter.
* Selser failures are false negatives.

Change-Id: Iaca49583994cc27803887e081740f231299f99a9