Add upload.py logic to skip authentication
Add upload.py logic to skip authentication

Clients of upload.py (like chromium's git-cl) can instantiate
HttpRpcServer with auth_function=None to bypass authentication
logic / prompts

Review: https://codereview.appspot.com/11915043

nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra