Merge "Revert "ConnectivityManager: no double NetworkCallback registration" because oit caused regressions http://b/35955593, http://b/35921499."
am: 704520c392

Change-Id: Ia0ae78f8406b81377491407cf5ef8ca339952def
tree: 9eef88c04f25f1281c680f09f24412776232d458
  1. core/
  2. services/
  3. tests/