test: add tls write error regression test

Add a mock TLS socket implementation and a regression test for
the previous commit.

This is to prevent v8.x from becoming susceptible to CVE-2018-7162.

Refs: https://github.com/nodejs-private/security/issues/189
PR-URL: https://github.com/nodejs-private/node-private/pull/131


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Evan Lucas <evanlucas@me.com>