Disable X-Forwarded-For in IPAuthenticationProvider by default

Disable X-Forwarded-For header check in IPAuthenticationProvider by default to improve reliability in client IP address detection. 

X-Forwarded-For is not a standard header, it's not required and not needed unless ZooKeeper is behind a proxy server. Relying on that when detecting client IP address should be the exception, not the standard behaviour. Therefore we should disable it by defult.