Do not throw exception if storage app data isolation is not enabled

As the feature is not enabled yet, we should not throw exception and
block all tests. We should show error message instead.

Bug: 213442885
Test: atest android.os.storage.cts.StorageManagerTest#testCallback
Change-Id: I9a46c9ed1aeb59d982ba3841943016bd7a357ac5
1 file changed