Fine tune RHEL repos

Disable all repos before explicitly enabling the expected ones: sometimes
active repos might be polluted (e.g. depending on the result of rhsm
auto-attach).

Enable Extras and Optional repos.

roles/rhel_subscribe/tasks/enterprise.yml

@@ -1,5 +1,10 @@
 ---
+- name: Disable all repositories
+  command: subscription-manager repos --disable="*"
+
 - name: Enable RHEL repositories
   command: subscription-manager repos \
                --enable="rhel-7-server-rpms" \
+               --enable="rhel-7-server-extras-rpms" \
+               --enable="rhel-7-server-optional-rpms" \
                --enable="rhel-7-server-ose-3.0-rpms"