docs(managing_deis): always stop platform before uninstalling

Author: carmstrong

docs/managing_deis/upgrading-deis.rst

@@ -28,7 +28,7 @@ Use the following steps to perform an in-place upgrade of your Deis cluster.
 
 .. code-block:: console
 
-    $ deisctl uninstall platform
+    $ deisctl stop platform && deisctl uninstall platform
     $ deisctl config platform set version=v0.15.0
     $ deisctl install platform
     $ deisctl start platform