When setting camera, ensure calling user is the same as logged in user.

When the VideoProvider API is used to change the camera, in addition to
performing permission checks on the caller, adding logic to ensure that
the calling UserHandle is the currently logged in User (this is to ensure
that a background app can't access the camera).

Test: Unit, manual
Bug: 32747443
Change-Id: I0856f991c520dd1f5fa0146919941c052cba8a01