Add mqtt.max_qos, use in AWS GG

This way max qos is persisted and applied correctly even after GG bootstrap.

PUBLISHED_FROM=52fa78f53872260fb4e600e17cc21576e31a989b

Author: Deomid Ryabkov

lib/cc3200/libmqtt.a

@@ -26,6 +26,7 @@ config_schema:
   - ["mqtt.keep_alive", "i", 60, {title: "Keep alive interval"}]
   - ["mqtt.will_topic", "s", "", {title: "Will topic"}]
   - ["mqtt.will_message", "s", "", {title: "Will message"}]
+  - ["mqtt.max_qos", "i", 2, {title: "Limit QoS of outgoing messages to at most this"}]
   - ["debug.stdout_topic", "s", "", {title: "MQTT topic to publish STDOUT to"}]
   - ["debug.stderr_topic", "s", "", {title: "MQTT topic to publish STDERR to"}]
 cdefs:

lib/cc3220/libmqtt.a

@@ -57,6 +57,7 @@ SLIST_HEAD(global_handlers, global_handler) s_global_handlers;
 static void mqtt_global_reconnect(void);
 
 void mgos_mqtt_set_max_qos(int qos) {
+  if (s_max_qos == qos) return;
   LOG(LL_INFO, ("Setting max MQTT QOS to %d", qos));
   s_max_qos = qos;
 }
@@ -283,6 +284,8 @@ bool mgos_mqtt_init(void) {
   }
   mgos_net_add_event_handler(mgos_mqtt_net_ev, NULL);
 
+  mgos_mqtt_set_max_qos(mgos_sys_config_get_mqtt_max_qos());
+
   mgos_hook_register(MGOS_HOOK_DEBUG_WRITE, s_debug_write_hook, NULL);
 
   return true;