Update Test924 to filter for messages related to test thread am: 1989aa4b39

Original change: https://android-review.googlesource.com/c/platform/art/+/2257701

Change-Id: I3ed6ed400f4be25848af2df71b8c01b2fa919d29
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>