Also inform activity manager that lock task packages changed

When user data is cleared in DevicePolicyManager, we clear the lock
task packages list. We should also forward that information to the
ActivityManager, so they can do relevant clean up; in particular this
will stop any running lock tasks.

Bug: 68688028
Test: manual
Change-Id: I0f40e7e08efd5ad2ca20b50ffa1032ddb13d1adb