registry: keygetter value fix

• register method of DictModuleAutoDiscoverySubRegistry class gives original value of parameter value to the keygetter method as well as the modified value from valuegetter.

• NOTE If your registry.py is using DictModuleAutoDiscoverySubRegistry and you use your own keygetter method then please update your keygetter method to use all three parameters.

Co-authored-by: Jan Åge Lavik <jan.age.lavik@cern.ch>
Co-authored-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
Signed-off-by: Graham R. Armstrong <graham.richard.armstrong@cern.ch>