With some modems, the lock/unlock of the SIM-ME interface with +CSIM=1/0
command is followed by #QSS unsolicited messages. With the current
implementation, this messages are mistaken for SIM swap events and so the
modem is first dropped and then re-probed.
With this patch, the plugin takes into account the SIM-ME lock state when
parsing #QSS unsolicited, so that the QSS handler can correctly
elaborate the messages that are not related to SIM swap events.