Description:
------------
Using DirectoryIterator on path that uses mergerfs[1] as underlying fs system causes the returned results to be duplicated.

Using other file system related scan function does not show the same problems. i.e. scandir works perfectly.

1: https://github.com/trapexit/mergerfs

Test script:
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php -r 'foreach( new DirectoryIterator('/path/to/mergerfs') as $it) echo $it->getFilename().PHP_EOL;'

Expected result:
----------------
dir1
dir2
dir3


Actual result:
--------------
dir1
dir2
dir3
dir1
dir2
dir3