Do not run hp-makeuri on network printers known to be non-HP

system-config-printer runs the command hp-makeuri of HPLIP on all
detected network printers to check whether they are supported by
HPLIP. Only HP printers are supported by HPLIP and so it does not make
sense to run this command on any other manufacturer's
printer. Unfortunately this does not always simply give a negative
answer but sometimes hp-makeuri hangs indefinitely (Ubuntu bug
call it any more now if we know if the printer is not from HP.
Handle pending Gtk events to close the search dialog (bug #1052203).