Move net-test-utils to its own directory am: 0fb2de46f0 am: 3d9ec0a4b8

Original change: https://android-review.googlesource.com/c/platform/frameworks/libs/net/+/1654919

Change-Id: Ic7f068d3f9729bb437d0b8dc0ff2c3df4b9d9434
tree: 1005b88fd25d9b375f5c9b5fc73f60342a88beb3
  1. staticlibs/