Avoid updating class loaders outside system weaks am: f3c44b4109 am: e2a6a647a1

Original change: https://android-review.googlesource.com/c/platform/art/+/2242213

Change-Id: I0e6f201a530f91381648d9ac2292c5999534b422
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>