lib: make tls.checkServerIdentity() more strict

Incorporates changes from commit e3452535 ("tls: better error reporting
at cert validation") to test/simple/test-tls-check-server-identity.js
to make back-porting the patch easier.

CVE-2016-7099

PR-URL: https://github.com/nodejs/node-private/pull/62


Reviewed-By: Rod Vagg <rod@vagg.org>