CatService: Correct Open Channel handling.

STK open channel command requests are communicated to the
telephony framework via an UNSOL_STK_EVENT_NOTIFY followed by
UNSOL_STK_CALL_SETUP pair of RIL messages.

This communication is distinct from a proactive command
since the card is only looking to notify the framework
of an action that the modem will handle on its own.

Thus, we need to adjust the conditional block properly to
catch this situation and send the appropriate response
back to RIL.

Change-Id: If29911d9b1d0d6c6b1213abc644fff57cf3d7398
CRs-Fixed: 580669