Skip loading credentials for save-python-settings-file (#1008)

* Skip loading credentials for save-python-settings-file

Loading AWS Credentials and creating AWS Client classes take a lot of
time. We do not need to do that for the save-python-settings-file
command.

* change list to tuple (list unnecessary)

---------

Co-authored-by: monkut <shane.cousins@gmail.com>

zappa/cli.py

@@ -475,7 +475,7 @@ def positive_int(s):
         else:
             self.stage_env = self.vargs.get("stage_env")
 
-        if args.command == "package":
+        if args.command in ("package", "save-python-settings-file"):
             self.load_credentials = False
 
         self.command = args.command