ThemeManager: Needs to use android.uid.system

The android.uid.system needs to be used for devices using a selinux kernel.
This should not cause issues with any other devices with non-selinux kernels.

Change-Id: I04d748d440ebafecbe94343a029c186a180ef13c
Merge "ThemeManager: Needs to use android.uid.system" into du44