etw: fix descriptors of events 9 and 23

Event 9 must include the string terminator in the last descriptor.
Event 23 must be published with no descriptors, in accordance with
the manifest.

PR-URL: https://github.com/nodejs/node/pull/5742


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>