improve getSocketCookie() am: 30354a0174

Original change: https://android-review.googlesource.com/c/platform/frameworks/libs/net/+/2452665

Change-Id: I5d25db198734cac86463d07d259b3138e2417e90
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>