Add tests for default storage class properties
Created by: tonifinger
This PR adds a test for the K8s default storage class.
A user can either run the test script by providing their Kubernetes cluster config, or use it as a Sonobuoy plug-in, in order to check the default storage class of a cluster. Following tests are implemented:
- Check if a default storage class is defined
- Check if the default storage class has set a provisioner
- Check if ReadWriteOnce is set as the supported access mode
This PR also adds configuration files to create the Docker image and plugin description in such a way that they can be executed by sonobuoy. Closes #289