Make objects.Flavor._orig_projects a list

The projects field is a list type but the init was
defaulting it to an empty dict. This simply makes it
a list.

This was apparently not causing any problems, but it's
not correct so we might as well fix it.

Change-Id: If22514f79e5e45b15e3b777c89713f7014112d99

nova/objects/flavor.py

@@ -48,7 +48,7 @@ class Flavor(base.NovaPersistentObject, base.NovaObject):
     def __init__(self, *args, **kwargs):
         super(Flavor, self).__init__(*args, **kwargs)
         self._orig_extra_specs = {}
-        self._orig_projects = {}
+        self._orig_projects = []
 
     @staticmethod
     def _from_db_object(context, flavor, db_flavor, expected_attrs=None):