[5.2] Optimize Filesystem moveDirectory

[bepsvpt]

When move directory with overwrite flag, the first step is deleting the target directory.

In the delete step, we should check the return value, we could go on if it succeed.

After deleting the target directory, we use rename function to move the directory instead of coping and deleting.

[JoostK]

Oh look, the line below does exactly the same 😉 You may therefore just drop the rename inside the if statement 👍

It is also possible to condense the nested if-clause into the first, however keeping it like this is clearer as it separates the condition from the action.