Fix HttpRequester threading issues
Fix HttpRequester threading issues

Locking on this is futile if the object to be protected has static scope.
Also increases efficiency through double check locking

AngleSharp/AngleSharp,FlorianRappl/AngleSharp,AngleSharp/AngleSharp,FlorianRappl/AngleSharp,AngleSharp/AngleSharp,AngleSharp/AngleSharp,AngleSharp/AngleSharp,FlorianRappl/AngleSharp,FlorianRappl/AngleSharp