Properly set default voice interactor

We need to figure out the default voice interactor to give
it default permissions. This happens before the user has
been unlocked and if the voice interactor is not direct
boot aware we fail to find it, hence no permissions are
granted. Now we query the package manager for both direct
boot aware and unaware components. This is fine as we
don't interact with the assistant until the user is
unlocked.

bug:28963642

Change-Id: Ide5471fa1798e868c6e3a4b5e87570a5556e2d3f