Persist changes to policy changed flags

We have to mark the AppPermissions as "delayChanges" so that later
app.persistChanges does anything.

Fixes: 127285797
Test: atest CtsDevicePolicyManagerTestCases:com.android.cts.devicepolicy.MixedDeviceOwnerTest#testPermissionGrant
Change-Id: I5ae04fc0db8e9b9d81f8c32bd9a5e585b58df716