Merge "libprocessgroup: Check validity of uid and pid arguments" am: c1798def91 am: f5d65bf11c am: 92824d9d04

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

Change-Id: I245c9c521391386acee8c16dcb15d5cc08edb06e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>