RPCMuon bugfix in MuonIdProducer

The RPCMuon is mis-implemented as a subset of TrackerMuons.
Originally it is designed to be a complementary ones to the TM's.
Since it's a mix of two possible types now, I think the type should not be set only right after the flags goodTrackerMuon and goodRPCMuon are computed.
Otherwise there's going to be confusion later.