Drop log level to TRACE

For people not using driver networks these log lines would just be
confusing.

client/task_runner.go

@@ -1446,13 +1446,13 @@ func (r *TaskRunner) startTask() error {
 			r.logger.Printf("[INFO] client: alloc %s task %s auto-advertising detected IP %s",
 				r.alloc.ID, r.task.Name, sresp.Network.IP)
 		} else {
-			r.logger.Printf("[DEBUG] client: alloc %s task %s detected IP %s but not auto-advertising",
+			r.logger.Printf("[TRACE] client: alloc %s task %s detected IP %s but not auto-advertising",
 				r.alloc.ID, r.task.Name, sresp.Network.IP)
 		}
 	}
 
 	if sresp.Network == nil || sresp.Network.IP == "" {
-		r.logger.Printf("[DEBUG] client: alloc %s task %s could not detect a driver IP", r.alloc.ID, r.task.Name)
+		r.logger.Printf("[TRACE] client: alloc %s task %s could not detect a driver IP", r.alloc.ID, r.task.Name)
 	}
 
 	// Update environment with the network defined by the driver's Start method.