Fix behaviour change in recent commit bbc1dc6 so that SynchronousRestObjectRequester.MakeRequest() calls with no timeout specified use the default HttpWebRequest timeout as previously.

I mistakenly thought that that default request timeout was inifite rather than 100 seconds, restoring previously behaviour.
As per http://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.timeout%28v=vs.100%29.aspx
Relates to http://opensimulator.org/mantis/view.php?id=7165