Allow the device initializer to perform user setup tasks.

A device initializer is an application that is allowed to run
during user provisioning on device owner devices. During
device provisioning (or, user provisioning of the first user
of the device), a device initializer is granted device owner
permissions. During secondary user provisioning, a device
initializer is granted profile owner permissions. Once
provisioning is complete for a user, all elevated permissions
are removed from the device initializer and the device admin
component of the app is disabled.

Bug: 19230954
Change-Id: Ib6725fb3b09bb21e4198a5dc0b445ccebb40b27e