Fix bluetooth tethering on multi-user

Bluetooth runs as UID 1001002 when on a secondary user. With this change
the NetworkStack verifies that the calling UID matches the Bluetooth app
regardless of the user.

Test: flashed, BT reverse tethering still working as primary user
      (no option to turn on as secondary user on phones)
Bug: 123655057
Change-Id: I23f9c5fa40f3bb676ac65dd8c15106c9d78309a4