mount-android-partitions: Probe for schedtune nesting ability
mechanicd would like to take advantage of the non-systemd managed schedtune cgroup present in certain generations of Android kernels. To do that the schedtune cgroup needs to be probed for functionality of nesting cgroups inside of each other, as that is what our Halium container does. Without this nesting patch [1] it fails to initialize the LXC container. So for the sake of having the functionality available on patched kernels, probe whether nesting of cgroups works properly, and unmount schedtune if not.