This is a followup to #4699 that addresses an oversight that could cause
the CRI to relabel the host /dev/shm, which should be a no-op in most
cases. Additionally, fixes unit tests to make correct assertions for
/dev/shm relabeling.
Discovered while applying the changes for #4699 to containerd/cri 1.4:
https://github.com/containerd/cri/pull/1605
Signed-off-by: Jacob Blain Christen <jacob@rancher.com>
