Handle 'UNSOL_STK_EVENT_NOTIFY' without 'SETUP_MENU'.

Set the CurrentCmd to MainCmd after launching the event
message, while handling UNSOL_STK_EVENT_NOTIFY in StkAppService.
This ensures the CurrentCmd still points to SEND_SMS instead of
SET_UP_MENU till the launching of event message.
This is done to take care of null pointer exception, which can occur
in case where there is no prior SET_UP_MENU proactive command exists,
while STK event notify is sent.

Change-Id: I971740add8aca1200add4e2222c52b59704dd4a2
CRs-Fixed: 602357
Merge "Handle 'UNSOL_STK_EVENT_NOTIFY' without 'SETUP_MENU'." into cm-11.0