Merge "Replace BaseNetworkObserver with BaseNetdUnsolicitedEventListener" am: fcfec6bf2e am: a549488125

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I4039814ea4c48bdaf7e54dbf3d1242a18235ee7b