Mms: Fix SMS is not sent in ECBM unless click send again

When clicking "yes" button on "Emergency Callback Mode" dialog,
EmergencyCallbackModeExitDialog.onDismiss() function will be called
and set the "exit_ecm_result" to false. Thus, after back to
ComposeMessageActivity, the message can't be sent.

Change to listen the AlertDialog's onCancel event instead.

Change-Id: Icf2e9a4b5e80c7901b0842c13c12a2dded28f50e
1 file changed