Merge "groupNetworkStats - switch ->at() to []" am: 7f21334959

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2541491

Change-Id: Ifd33d65486b3dd891fcb97a28a8b346de161a917
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>