Clean up split system user code for device policy management

Bug: 137101239
Test: build, sync and reboot
m update-api -j64 && m
atest FrameworksServicesTests:com.android.server.devicepolicy.DevicePolicyManagerTest

Merged-In: Ibc642c04d3dcba84cd9837efb09cde04b46ff620
Change-Id: Ibc642c04d3dcba84cd9837efb09cde04b46ff620
(cherry picked from commit 8f9193aed0ab9a72e7e30ecd4ea06fae0136fc18)
3 files changed