src: fix delete operator on vm context

In the implementation of the vm module,
if a property is successfully deleted
on the sandbox, we also need to delete it
on the global_proxy object. Therefore, we
must not call args.GetReturnValue().Set().

We only intercept, i.e., call
args.GetReturnValue().Set(), in the
DeleterCallback, if Delete() failed, e.g. because
the property was read only.

PR-URL: https://github.com/nodejs/node/pull/11266


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>