Support Odoo version auto-discovery via HTTPS

ConnectorXMLRPC always uses HTTP when auto-discovering the Odoo version.

If the service is running on HTTPS, the auto-discovery fails and the url is set to None. ConnectorXMLRPCSSL then tries to rewrite the url from HTTP to HTTPS but fails because the url is set to None.

A work-around when using the library is to explicitly set the version when creating a connection.  That works for me.

But for future versions of the library, something like the attached would be an easy (as yet untested) means to support auto-discovery via HTTPS.