Reduce the scope for expensive computation for checking hidden dir

Hidden files check is expensive and not required when MediaProvider is
the caller.
Bug: 184608308
Test: atest android.scopedstorage.cts.host.LegacyStorageHostTest#testInsertHiddenFile

Change-Id: I93839a9d66d7caa132e337275a5553ec7f4f635a
1 file changed