Red Hat changed the repository names/labels for
Satellite Client repository in Satellite 6.11 and
above, See: https://access.redhat.com/solutions/7004377
This change updates the satellite_repo URL's to use the
new labels.
Also adds environment variable REG_SAT_REPO to allow the
user to override the repository label.
Closes-Bug: #2013451
Change-Id: I6c2a93658213644140caf0e4a8c910b1af22cd1c
