Reverse a bad decision in r93820, which added a comment to WebRequest::getFullRequest...

Reverse a bad decision in r93820, which added a comment to WebRequest::getFullRequestURL() saying it would return protocol-relative URLs if $wgServer is protocol-relative. This behavior makes no sense, though, and most callers expect fully qualified URLs. So make it return a fully qualified URL and update the one caller that expected the return value would be compatible with getFullURL()