added documentation for the new reuth option in docker registry configuration

also fixed a typo in the new code where I used cred instead of creds

salt/modules/dockerng.py

@@ -55,6 +55,7 @@ be used, it is recommended to place this configuration in :ref:`Pillar
         email: <email_address>
         password: <password>
         username: <username>
+        reauth: <boolean>
 
 For example:
 
@@ -66,6 +67,18 @@ For example:
         password: s3cr3t
         username: foo
 
+Reauth is an optional parameter that forces the docker login to reauthorize using
+the credentials passed in the pillar data. Defaults to false. For example:
+
+.. code-block:: yaml
+
+    docker-registries:
+      https://index.docker.io/v1/:
+        email: foo@foo.com
+        password: s3cr3t
+        username: foo
+        reauth: True
+
 Mulitiple registries can be configured. This can be done in one of two ways.
 The first way is to configure each registry under the ``docker-registries``
 pillar key.
@@ -954,7 +967,7 @@ def _image_wrapper(attr, *args, **kwargs):
                     password=creds['password'],
                     email=creds.get('email'),
                     registry=registry,
-                    reauth=cred.get('reauth', False))
+                    reauth=creds.get('reauth', False))
         except KeyError:
             raise SaltInvocationError(
                 err.format('Incomplete', ' for registry {0}'.format(registry))