ns_server and cbauth should support REVRPC JSON-RPC over HTTPS

The addition of support for encryption level strict causes problems for tools such as cbindex, cbevent, etc in that they establish a revrpc JSON-RPC connection with ns_server and this must currently be over HTTP. These tools should probably be written using a simple REST API client against the server instead of a revrpc client, however, it's a good idea to support JSON-RPC over HTTPS anyway. We should probably support both the case where the server cert should be verified not verified, which makes things a little bit complicated.