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

This reverts commit faa70976b490116323107166f90fdd944c5bdc77.

Change-Id: I86c07c113f24753be7c977e6d7f570b99391e1b5
2 files changed