Merge "Add a method to help mocking registerNetworkAgent" into main am: 13a5d4b36e am: 684e8d273d

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3543704

Change-Id: I287387c7119c58e12ed7d7fd06bed01f614a64e2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>