Message Reject notification shouldn't be shown in Emergency Calling Mode

Issue: While in emergency mode, if we receive a message, there is a notification
being shown as "Text Message rejected".

Fix: In CdmaSMSDispatcher.java, send RESULT_OK response instead of RESULT_SMS_GENERIC_ERROR
for messages during Emergency mode. So, that SMS_REJECTED action is not broadcasted.

If the result is RESULT_OK from CdmaSMSDispatcher, the function notifyAndAcknowledgeLastIncomingSms()
is not called from SMSDispatcher.java and hence SMS_REJECTED_ACTION intent is not broadcast.
Consequently SMSRejectReceiver.java will not receive the broadcast and will not show reject
notification.

Change-Id: I2aa8f239393b3e6eeac6b0c2bb69799018e9ae9d