test: configure certs in tests

OpenSSL 1.1.0 disables anonymous ciphers unless building with
enable-weak-crypto. Avoid unnecessary dependencies on these ciphers in
tests.

PR-URL: https://github.com/nodejs/node/pull/16130


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rod Vagg <rod@vagg.org>