test: fix test-process-active-wraps.js

b636ba81 caused a regression
on Windows due to the way server handles are cleaned up. This
commit fixes the test by allowing the handle to be cleaned up.

Fixes: https://github.com/joyent/node/issues/8986
PR-URL: https://github.com/joyent/node/pull/8998


Reviewed-By: Julien Gilli <julien.gilli@joyent.com>
Reviewed-By: Bert Belder <bertbelder@gmail.com>