Don't copy ringtones when profile sync goes off

Experimentally, it makes more sense to more people to have the parent
setting as an overlay not a concrete thing.

Test: make cts -j30 && cts-tradefed run cts --module CtsDevicePolicyManagerTestCases --test 'com.android.cts.devicepolicy.ManagedProfileTest#testRingtoneSyncAutoDisableRingtone' </dev/null 2>&1
Bug: 34730524
Change-Id: I5f804713def9e54921b90e4f5cea742ba8aaa685