Support for Satellite Capsule in rhel-registration

For deployments running on RHEL with Satellite 6 (or beyond) with
Capsule (Katello API enabled), the Katello API is available
on 8443 port, so the previous API ping didn't work for this case.

Capsule is now supported since we just check if katello-ca-consumer-latest
rpm is available to tell that Satellite version is 6 or beyond.

Closes-Bug: #1716777
Change-Id: If76763b367917fc15f609ad144679750602826eb
(cherry picked from commit ad3ea5bb7a2ee2cb1ae6b1d21b2f0b5a177c9fc6)