Allow to use JNLP instead of ssh for Jenkins orka plugin to attach orka VMs as Jenkins agents.

For security reason, ssh traffic may not be allowed from the Jenkins instances network to the MacStadium network. Please enable agent attached to Jenkins instance via JNLP. One example is Jenkins k8s plugin. It provisions k8s pod and the pod has slave.jar running and register itself as a Jenkins agent. We want to do the same with orka VMs so no ssh traffic is needed between Jenkins instances and MacStadium orka VMs.