BZ#1134610 - multiple repos in subscription_manager_repos

https://bugzilla.redhat.com/show_bug.cgi?id=1134610

The code for adding repos uses subscription-manager and the argument
formatting was taken from code using yum-config-manager, but
subscription-manager expects differently formatted arguments than
yum-config-manager. This commit commit fixes the argument formatting
to be compatible with subscription-manager.