Merge "Revert "Return the registry in registerNetworkAgent."" into main am: 82c551e08e am: 60670b309d

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3535263

Change-Id: If884ce604efba5d2eb53dbe91f833157cc259e9d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>