stasis: add functions embarrassingly missing from r400522

I neglected to implement two of the endpoint subscription functions when
I did the work. Normally, you'll only hit that when you unsubscribe from
a specific endpoint.
........

Merged revisions 402276 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@402277 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/stasis/app.c

@@ -934,3 +934,19 @@ int app_subscribe_endpoint(struct app *app, struct ast_endpoint *endpoint)
 		return 0;
 	}
 }
+
+int app_unsubscribe_endpoint_id(struct app *app, const char *endpoint_id)
+{
+	if (!app || !endpoint_id) {
+		return -1;
+	}
+
+	return unsubscribe(app, "endpoint", endpoint_id);
+}
+
+int app_is_subscribed_endpoint_id(struct app *app, const char *endpoint_id)
+{
+	RAII_VAR(struct app_forwards *, forwards, NULL, ao2_cleanup);
+	forwards = ao2_find(app->forwards, endpoint_id, OBJ_SEARCH_KEY);
+	return forwards != NULL;
+}