Add mount propagation option to emptyDir volumes
What does this MR do?
Add mount propagation option to emptyDir volumes, add some very basic testing for the setting as there was previously none
Why was this MR needed?
Mount propagation was already supported on hostPath and PVC type volumes, but not on emptyDir. Allowing this to be optionally set by the operator unlocks some advanced configurations that the operator may require.
In our current scenario, we mount an emptyDir on the kubernetes executor and use bi-directional mount propagation to propagate an overlay mount across all containers. Currently the only way to work around the limitation of this missing option is with a complex mutation webhook, which can be completely avoided by simply making this configurable.
What's the best way to test this MR?
Set mount_propagation in an emptyDir volume, verify mountPropagation is successfully added to the podSpec for the configured mount.