More comprehensive client proxy queue guards (#3414)

* More comprehensive MQTT thread and queue guards

* Consolidate logic

* Remove channel check

* Check for map_reporting_enabled as well

* Update message

* Remove channel check from here as well

* One liner

* Start the mqtt thread back up when channels change and we want mqtt

src/mesh/Channels.h

@@ -105,6 +105,9 @@ class Channels
     // Returns true if we can be reached via a channel with the default settings given a region and modem preset
     bool hasDefaultChannel();
 
+    // Returns true if any of our channels have enabled MQTT uplink or downlink
+    bool anyMqttEnabled();
+
   private:
     /** Given a channel index, change to use the crypto key specified by that index
      *