Let users disable create_preload_data if it isn't necessary

The demo things might not be desirable in a production environment.

installer/roles/kubernetes/defaults/main.yml

@@ -1,5 +1,6 @@
 ---
 dockerhub_version: "{{ lookup('file', playbook_dir + '/../VERSION') }}"
+create_preload_data: True
 
 admin_user: 'admin'
 admin_email: 'root@localhost'

installer/roles/kubernetes/tasks/main.yml

@@ -192,6 +192,7 @@
       bash -c "awx-manage create_preload_data"
   register: cdo
   changed_when: "'added' in cdo.stdout"
+  when: create_preload_data | bool
 
 - name: Delete management pod
   shell: |