Removes the use of mutables as default args

Removes the use of mutables as default args

Passing mutable objects as default args is a known Python pitfall.
We'd better avoid this. This commit changes mutable default args with
None, then use 'arg = arg or {}', 'arg = arg or []'. For unit code which
doesn't use the args , just set with None. This commit also adds hacking
check.

This code was taken from commit 0bea84ac20fe498bd08f7212a0017196c8cb0812
in Nova.

Change-Id: I36d07cade687690dc02a8f6cc3d70f5d00caf112
Co-Authored-By: ChangBo Guo(gcb) <glongwave@gmail.com>