Allow processes in the "system" group to read /metadata/ota. am: a71faae86f am: f0c99ee9c7 am: bac6593a1e

Original change: https://android-review.googlesource.com/c/platform/system/core/+/2656857

Change-Id: I11ed3e0dbba936e698f83ee73c4837d7339c17bd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>