Fix init method for HasStandardAttributes

Puttting description in the signature of __init__ would make it
consume the first positional argument that was passed in. This
would lead to a difficult to understand traceback from sqlalchemy
when the object was initialized with a positional.

This correctly checks the kwargs for the description and any other
standard attributes rather than leaving it in a positional.

Closes-Bug: #1614897
Change-Id: I264bf5fbfc834d7f5d86a2ad03f5e68a91e2185c

neutron/db/model_base.py

@@ -194,11 +194,17 @@ class HasStandardAttributes(object):
                                 single_parent=True,
                                 uselist=False)
 
-    def __init__(self, description='', *args, **kwargs):
+    def __init__(self, *args, **kwargs):
+        standard_attr_keys = ['description', 'created_at',
+                              'updated_at', 'revision_number']
+        standard_attr_kwargs = {}
+        for key in standard_attr_keys:
+            if key in kwargs:
+                standard_attr_kwargs[key] = kwargs.pop(key)
         super(HasStandardAttributes, self).__init__(*args, **kwargs)
         # here we automatically create the related standard attribute object
         self.standard_attr = StandardAttribute(
-            resource_type=self.__tablename__, description=description)
+            resource_type=self.__tablename__, **standard_attr_kwargs)
 
     @declarative.declared_attr
     def description(cls):