allow python-rhsm to talk to RCS

RCS is a service that returns entitlement certs that are valid for one hour.
The new SpliceConnection class allows subscription-manager to talk to RCS, in
order to retrieve entitlement certs.

This patch is to support changes made in subscription-manager that I didn't make a pull request for yet.. If you want to try out the patch against a real RCS, I can provide a demo machine that's already set up.