Bug $pref::Net::RegionMask

Serverquery.cc uses this in pickMasterServer() function but $pref::Net::RegionMask is not defined anywhere in prefs or mentioned anywhere else in script or code.

Reading the code in pickMasterServer() seems to imply that it should rather be using $pref::Server::RegionMask which is defined and used in the scripts.

I don't know what the background is of having both RegionMask variables but it seems that something dropped out along the way.