Merge "Replace BaseNetworkObserver with BaseNetdUnsolicitedEventListener" am: fcfec6bf2e

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1547454

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Idd7f8fe597639f334e5d99c23ab570a751f8d9d6