Fix modem list query

Modem list is no longer available immediately after QOfonoManager has been constructed (as a result of elimination of blocking D-Bus calls). One has to wait for modemsChanged or defaultModemChanged signal.

Also, removed QOfonoModem and other unnecessary members from CDSimController, normalized signal and slot names.
It is dirty. But IMO better than making contactsd test a friend of an internal libqofono class. That would be even dirtier.