Query DinD instances for running containers and list the published ports

so the user can reverse proxy to the instance/port easily.

services/check_used_ports_task.go

@@ -0,0 +1,10 @@
+package services
+
+type checkUsedPortsTask struct {
+}
+
+func (c checkUsedPortsTask) Run(i *Instance) {
+	if ports, err := GetUsedPorts(i); err == nil {
+		i.Ports = ports
+	}
+}