doc swift service start issues with no ring

fixes bug 996944

As in the bug report, users following this guide exactly
will encounter a failed service start at this point in the
manual. This isn't a big problem - the ring files just need to be
copied first.

Rather than significantly changing the flow of the docs, this change
adds a simple warning so that first-time users aren't alarmed.

Change-Id: Ibaff34a14e7d82f674b6fe9b47923f7465d8825b

doc/src/docbkx/openstack-install/install-config-storage-nodes.xml

@@ -145,6 +145,14 @@ swift-init account-server start
 swift-init account-replicator start
 swift-init account-auditor start</programlisting>
             </para>
+        <warning><title>Don't Panic</title><para> If you are
+        following these instructions in a linear manner, at this
+        point the ring files may not be present on the storage
+        nodes. This may cause some of the services such as the
+        *-replicator to fail to start. After you have created the
+        ring files and distributed them to the storage nodes, a
+        service restart should allow these to start.
+        </para></warning>
         </listitem>
     </orderedlist>
 </section>