Jailer: Allow 'none' device for cgroups
Jailer: Allow 'none' device for cgroups

According to the cgroups man page, the device used in the mount point
can be 'none'. Modify the regex used in the jailer to also match that.

Signed-off-by: Andrei Cipu <a96f49656a95c9ed8a752b21dcae83fc326fba28@amazon.com>

firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker