stream_base,tls_wrap: notify on destruct

The TLSWrap constructor is passed a StreamBase* which it stores as
TLSWrap::stream_, and is used to receive/send data along the pipeline
(e.g. tls -> tcp). Problem is the lifetime of the instance that stream_
points to is independent of the lifetime of the TLSWrap instance. So
it's possible for stream_ to be delete'd while the TLSWrap instance is
still alive, allowing potential access to a then invalid pointer.

Fix by having the StreamBase destructor null out TLSWrap::stream_;
allowing all TLSWrap methods that rely on stream_ to do a check to see
if it's available.

While the test provided is fixed by this commit, it was also previously
fixed by 478fabf3. Regardless, leave the test in for better testing.

PR-URL: https://github.com/nodejs/node/pull/11947


Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>