Fix GraphicsStats#findRootPath and disable CacheManager#trimMemory tests am: 24921a0325

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2379069

Change-Id: Icab9f94d9edcb350a5ed7bc52969c06200cdb589
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>