Create cgoup recursively to workaround systemd deleting cgroups_root.

This is my case:

My cgroups_root of mesos-slave is some_user/mesos under /sys/fs/cgroup。

It happens that this some_user dir may be gone for some unknown reason, in which case I can no longer create any cgroup and any task will fail.

So I would like to change 

Try<Nothing> create = cgroups::create(
hierarchy,
infos[containerId]->cgroup);

to

Try<Nothing> create = cgroups::create(
hierarchy,
infos[containerId]->cgroup,
true);

in CgroupsIsolatorProcess::prepare in src/slave/containerizer/mesos/isolators/cgroups/cgroups.cpp.

However, I'm not sure if there's any potential problem doing so. Any advice?