Pass existing object references within access methods

This avoids re-loading objects from the database in our
chain of permission checking, wherever possible.
access.py is equiped to handle object references instead
of pk ints, and permissions.py is changed to pass those refs.

awx/main/utils/common.py

@@ -724,7 +724,10 @@ def get_pk_from_dict(_dict, key):
     Helper for obtaining a pk from user data dict or None if not present.
     '''
     try:
-        return int(_dict[key])
+        val = _dict[key]
+        if isinstance(val, object) and hasattr(val, 'id'):
+            return val.id  # return id if given model object
+        return int(val)
     except (TypeError, KeyError, ValueError):
         return None