BYO playbook fix

- Fix bug where playbooks/byo/config.yml would error if only a master is
  defined in the inventory.

playbooks/byo/config.yml

@@ -1,6 +1,8 @@
 ---
 - name: Run the openshift-master config playbook
   include: openshift-master/config.yml
+  when: groups.masters is defined and groups.masters
 
 - name: Run the openshift-node config playbook
   include: openshift-node/config.yml
+  when: groups.nodes is defined and groups.nodes and groups.masters is defined and groups.masters