Add new permission for am.updateLockTaskPackages()

Adds android.permission.UPDATE_LOCK_TASK_PACKAGES, available only to
the system and setup wizard, providing access to
updateLockTaskPackages() without registering with the device policy
manager as a device owner.

Bug: 20016740
Change-Id: I6eceb5cece9407c84eabf3a818bb908f95989b91