Clear calling identity in registerNetworkAgent. am: 4b1cd16a76 am: 964f7c7e4d am: 7c00b2f055

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1511317

Change-Id: I6aee037648415475a53053d1bcf015227cf8ec96
tree: 6de962923d5f54962e3f50aa848989843a72312c
  1. core/
  2. services/
  3. tests/