#42 Crash when not using rex authentication

[Heikki]

Server reports exception when trying to login without using rex authentication:
An unhandled exception of type 'System.UriFormatException' occurred in System.dll

Additional information: Invalid URI: The hostname could not be parsed.

in Util::SendXmlRpcCommand().

Scene:AddNewClient() doesn't check first for rex authentication mode when trying to retrieve permission information from authentication server.