'Finds the hash for a config.
Calls sub_dict, which is a recursive method which sorts lists which may be buried in the structure.
Dumps the config to json with sort_keys set.
Grabs an MD5 hash.
:param config: dict describing item
:return: 32 character string (MD5 Hash)'

def hash_config(self, config):

    item = sub_dict(config)
    item_str = json.dumps(item, sort_keys=True)
    item_hash = hashlib.md5(item_str)
    return item_hash.hexdigest()
