Add slide #11 of upstream training

Change-Id: I9c1e99071ce19dc24d895ae88817c636543ce061

doc/upstream-training/11-devstack.rst

@@ -0,0 +1,32 @@
+devstack.org
+============
+
+.. image:: ./_assets/11-01-devstack.png
+
+----
+
+rejoin-stack.sh
+===============
+
+.. image:: ./_assets/11-02-rejoin-stack.png
+  :width: 75%
+
+----
+
+http://localhost/
+=================
+
+.. image:: ./_assets/11-03-http-localhost.png
+  :width: 100%
+
+----
+
+.. image:: ./_assets/11-04-git.png
+
+----
+
+Exercise
+========
+
+Get the code for the targeted contribution
+