crypto: support OPENSSL_CONF again

A side-effect of https://github.com/nodejs/node-private/pull/82
was to remove support for OPENSSL_CONF, as well as removing the default
read of a configuration file on startup.

Partly revert this, allowing OPENSSL_CONF to be used to specify a
configuration file to read on startup, but do not read a file by
default.

If the --openssl-config command line option is provided, its value is
used, not the OPENSSL_CONF environment variable.

Fix: https://github.com/nodejs/node/issues/10938
PR-URL: https://github.com/nodejs/node/pull/11006


Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>