OBS-427: Support verify_certs with self-issued certs for elastic cloud

[relud]

This only impacts https urls, which right now we only use for elastic cloud.

In stage we are currently depending on verify_certs=False to connect to elastic cloud, and this will allow us to instead use a certs.pem provided by elastic cloud to verify their https certs.

[smarnach]

The code changes are looking good – it's basically just a new configuration setting that's passed through several layers of indirection.

I wonder whether there's a reasonable way to enable SSL in the local stack for testing purposes, and whether that's a useful thing to do.

[relud]

I wonder whether there's a reasonable way to enable SSL in the local stack for testing purposes, and whether that's a useful thing to do.

i could do it, but i'm inclined to think it's not that helpful.