test: skip/replace weak crypto tests in FIPS mode

FIPS 140-2 does not permit the use of MD5 and RC4, skip or tests
that use them, or substitute with stronger crypto where applicable.

PR-URL: https://github.com/nodejs/node/pull/3757


Reviewed-By: Fedor Indutny <fedor@indutny.com>
Reviewed-By: James Snell <jasnell@gmail.com>
Reviewed-By: Shigeki Ohtsu <ohtsu@iij.ad.jp>