Merge "libprocessgroup: Check validity of uid and pid arguments" am: c1798def91 am: f5d65bf11c

Original change: https://android-review.googlesource.com/c/platform/system/core/+/2475605

Change-Id: I0e5cd03f8e462f142723d2bb090a8f9be0ace9f8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>