test: skip pseudo-tty/no_dropped_stdio test

We had marked it as flaky but in some failures it hangs
and does not seem to timeout, and or is reported as
an error.

Also add prefix to status file as it was missing.

Also fix name of status file in testcfg.py. It
was pointing to message.status instead of
pseudo-tty.status.

PR-URL: https://github.com/nodejs/node/pull/8470


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>