Revert hardcoding of cgroup path. am: 4407735953 am: 27f6b42bfa

Original change: https://android-review.googlesource.com/c/platform/system/netd/+/1479738

Change-Id: I4b43865f81b41df7d338ea6fea44fc5f267e12ad
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>