Quickstart guide add inventory in pull command

Quickstart guide can be confusing when pulling images if not using
all-in-one deployment.
Ansible will try to pull images in localhost rather than target nodes.
Issue: https://ask.openstack.org/en/question/109026/kolla-ansible-pull-error/

Change-Id: Ib7e767ee814041d1939c49731092695485dd2870

doc/quickstart.rst

@@ -470,11 +470,11 @@ Restart Docker and ensure that Docker is running.
     systemctl restart docker
 
 The Kolla community builds and pushes tested images for each tagged release of
-Kolla. Pull required images with appropriate tags.
+Kolla. Pull required images with appropriate tags in target nodes.
 
 ::
 
-    kolla-ansible pull
+    kolla-ansible pull -i /path/to/all-in-one
 
 View the images.