When registering with Satellite 6 or the Customer Portal, the RHEL registration script (extraconfig/pre_deploy/rhel-registration/scripts/rhel-registration) should disable any "auto-attached" repositories before enabling the repos listed in the rhel_reg_repos parameter.  I.e., it should do the equivalent of:

# subscription-manager repos --disable=*
# subscription-manager repos --enable=... --enable=...

Currently these repos are left enabled, which can create conflicts when running updates.  For example, I have the following in environment-rhel-registration.yaml:

rhel_reg_repos: "rhel-7-server-rpms,rhel-7-server-extras-rpms,rhel-7-server-rh-common-rpms,rhel-ha-for-rhel-7-server-rpms,rhel-7-server-openstack-7.0-rpms"

But when I use my Red Hat Employee Subscription, I end up with all of these repos enabled on my overcloud nodes:

Repo ID:   rhel-rs-for-rhel-7-server-eus-rpms
Repo ID:   rhel-7-server-extras-rpms
Repo ID:   rhel-7-server-openstack-7.0-rpms
Repo ID:   rhel-sjis-for-rhel-7-server-rpms
Repo ID:   rhel-lb-for-rhel-7-server-htb-rpms
Repo ID:   rhel-sap-hana-for-rhel-7-server-rpms
Repo ID:   rhel-7-server-htb-rpms
Repo ID:   rhel-ha-for-rhel-7-server-eus-rpms
Repo ID:   rhel-sap-for-rhel-7-server-rpms
Repo ID:   rhel-7-server-rt-htb-rpms
Repo ID:   rhel-7-server-eus-rpms
Repo ID:   rhel-rs-for-rhel-7-server-rpms
Repo ID:   rhel-7-server-rpms
Repo ID:   rhel-7-server-rh-common-rpms
Repo ID:   rhel-ha-for-rhel-7-server-rpms
Repo ID:   rhel-ha-for-rhel-7-server-htb-rpms
Repo ID:   rhel-7-server-aus-rpms
Repo ID:   rhel-7-server-rt-rpms
Repo ID:   rhel-rs-for-rhel-7-server-htb-rpms
Repo ID:   rhel-7-server-rt-beta-rpms