Fix bug allowing an infinite subscribe loop (#348)

* Reset flag in each iteration of subscribe loop

FreeRTOS-Plus/Demo/coreMQTT_Windows_Simulator/MQTT_Basic_TLS/DemoTasks/BasicTLSMQTTExample.c

@@ -659,6 +659,9 @@ static void prvMQTTSubscribeWithBackoffRetries( MQTTContext_t * pxMQTTContext )
         xResult = MQTT_ProcessLoop( pxMQTTContext, mqttexamplePROCESS_LOOP_TIMEOUT_MS );
         configASSERT( xResult == MQTTSuccess );
 
+        /* Reset flag before checking suback responses. */
+        xFailedSubscribeToTopic = false;
+
         /* Check if recent subscription request has been rejected. #xTopicFilterContext is updated
          * in the event callback to reflect the status of the SUBACK sent by the broker. It represents
          * either the QoS level granted by the server upon subscription, or acknowledgement of

FreeRTOS-Plus/Demo/coreMQTT_Windows_Simulator/MQTT_Keep_Alive/DemoTasks/KeepAliveMQTTExample.c

@@ -713,6 +713,9 @@ static void prvMQTTSubscribeWithBackoffRetries( MQTTContext_t * pxMQTTContext )
         xResult = MQTT_ProcessLoop( pxMQTTContext, mqttexampleRECEIVE_LOOP_TIMEOUT_MS );
         configASSERT( xResult == MQTTSuccess );
 
+        /* Reset flag before checking suback responses. */
+        xFailedSubscribeToTopic = false;
+
         /* Check if the recent subscription request has been rejected. #xTopicFilterContext 
          * is updated in the event callback to reflect the status of the SUBACK
          * sent by the broker. It represents either the QoS level granted by the

FreeRTOS-Plus/Demo/coreMQTT_Windows_Simulator/MQTT_Mutual_Auth/DemoTasks/MutualAuthMQTTExample.c

@@ -779,6 +779,9 @@ static void prvMQTTSubscribeWithBackoffRetries( MQTTContext_t * pxMQTTContext )
         xResult = MQTT_ProcessLoop( pxMQTTContext, mqttexamplePROCESS_LOOP_TIMEOUT_MS );
         configASSERT( xResult == MQTTSuccess );
 
+        /* Reset flag before checking suback responses. */
+        xFailedSubscribeToTopic = false;
+
         /* Check if recent subscription request has been rejected. #xTopicFilterContext is updated
          * in the event callback to reflect the status of the SUBACK sent by the broker. It represents
          * either the QoS level granted by the server upon subscription, or acknowledgement of

FreeRTOS-Plus/Demo/coreMQTT_Windows_Simulator/MQTT_Plain_Text/DemoTasks/PlaintextMQTTExample.c

@@ -605,6 +605,9 @@ static void prvMQTTSubscribeWithBackoffRetries( MQTTContext_t * pxMQTTContext )
         xResult = MQTT_ProcessLoop( pxMQTTContext, mqttexamplePROCESS_LOOP_TIMEOUT_MS );
         configASSERT( xResult == MQTTSuccess );
 
+        /* Reset flag before checking suback responses. */
+        xFailedSubscribeToTopic = false;
+
         /* Check if recent subscription request has been rejected. #xTopicFilterContext is updated
          * in the event callback to reflect the status of the SUBACK sent by the broker. It represents
          * either the QoS level granted by the server upon subscription, or acknowledgement of

FreeRTOS-Plus/Demo/coreMQTT_Windows_Simulator/MQTT_Serializer/DemoTasks/SerializerMQTTExample.c

@@ -843,6 +843,9 @@ static void prvMQTTSubscribeWithBackoffRetries( Socket_t xMQTTSocket )
          * processing function everywhere to highlight this fact. */
         prvMQTTProcessIncomingPacket( xMQTTSocket );
 
+        /* Reset flag before checking suback responses. */
+        xFailedSubscribeToTopic = false;
+
         /* Check if recent subscription request has been rejected. #xTopicFilterContext is updated
          * in the event callback to reflect the status of the SUBACK sent by the broker. It represents
          * either the QoS level granted by the server upon subscription, or acknowledgement of