crypto: use CHECK instead in getSSLCiphers

The previous throws should never happen, and if they do, they
signal a larger issue in core. Make these checks rather than
throws.

PR-URL: https://github.com/nodejs/node/pull/16453


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>