node_contextify: do not incept debug context

node_contextify: do not incept debug context

Currently a debug context is created for various calls to util.

If the node debugger is being run the main context is the debug
context. In this case node_contextify was freeing the debug context
and causing everything to explode.

This change moves around the logic and no longer frees the context.

There is a concern about the dangling pointer

The regression test was adapted from code submitted by @3y3 in #4815

Fixes: https://github.com/nodejs/node/issues/4440
Fixes: https://github.com/nodejs/node/issues/4815
Fixes: https://github.com/nodejs/node/issues/4597
Fixes: https://github.com/nodejs/node/issues/4952
PR-URL: https://github.com/nodejs/node/issues/4815

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