Delete zombie sessions and instances (#71)

services/check_used_ports_task.go

@@ -1,12 +1,18 @@
 package services
 
+import "log"
+
 type checkUsedPortsTask struct {
 }
 
-func (c checkUsedPortsTask) Run(i *Instance) {
+func (c checkUsedPortsTask) Run(i *Instance) error {
 	if ports, err := GetUsedPorts(i); err == nil {
 		for _, p := range ports {
 			i.setUsedPort(p)
 		}
+	} else {
+		log.Println(err)
+		return err
 	}
+	return nil
 }