Comment 3 for bug 1678342

Description of problem:
It's not something that matters much right now, but as people will be moving to unified cgroup hierarchy, this will matter more.
/usr/lib/udev/snappy-app-dev hardcodes paths which are specific to legacy hierarchy (and assumes that devices controller is mounted...).

Version-Release number of selected component (if applicable):
snapd-2.23.6-1.fc27

Expected results:
All code which touches cgroups is ready for legacy and unified hierarchies.