Prevent message state from going to early states if it has reached the...

Prevent message state from going to early states if it has reached the delivered to user or displayed state.

coreapi/chat.c

@@ -144,8 +144,9 @@ static void _linphone_chat_room_destroy(LinphoneChatRoom *cr) {
 void linphone_chat_message_set_state(LinphoneChatMessage *msg, LinphoneChatMessageState state) {
 	/* do not invoke callbacks on orphan messages */
 	if (state != msg->state && msg->chat_room != NULL) {
-		if ((msg->state == LinphoneChatMessageStateDisplayed) && (state == LinphoneChatMessageStateDeliveredToUser)) {
-			/* If the message has been displayed we must not go back to the delivered to user state. */
+		if (((msg->state == LinphoneChatMessageStateDisplayed) || (msg->state == LinphoneChatMessageStateDeliveredToUser))
+			&& ((state == LinphoneChatMessageStateDeliveredToUser) || (state == LinphoneChatMessageStateDelivered) || (state == LinphoneChatMessageStateNotDelivered))) {
+			/* If the message has been displayed or delivered to user we must not go back to the delivered or not delivered state. */
 			return;
 		}
 		ms_message("Chat message %p: moving from state %s to %s", msg, linphone_chat_message_state_to_string(msg->state),