libprocessgroup: optimize SetAttributeAction::ExecuteForProcess performance am: 1e81ee1363

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/core/+/24271776

Change-Id: I9a9ec1f34199302ac89e2605c3839224cfbf62e4
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>