Test CSI plugin liveness probe

https://github.com/longhorn/longhorn/issues/3907

Test CSI plugin liveness probe should recover CSI socket file

Given healthy Longhorn cluster

When delete the Longhorn CSI socket file on one of the node(node-1). rm /var/lib/kubelet/plugins/driver.longhorn.io/csi.sock

Then the longhorn-csi-plugin-* pod on node-1 should be restarted.

And the csi-provisioner-* pod on node-1 should be restarted.
And the csi-resizer-* pod on node-1 should be restarted.
And the csi-snapshotter-* pod on node-1 should be restarted.
And the csi-attacher-* pod on node-1 should be restarted.

Note: In node-1, the other pods of the CSI sidecar components restarted are triggered by their internal ProbeForever to the CSI connection. It is not due to the liveness probe of the longhorn-csi-plugin.

And Longhorn CSI socket file should exist.

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