Description:
------------
is_dir fails on UNC filepaths on windows.  It is not a permissions problem since every other command works, and
there is a workaround (using opendir).

Reproduce code:
---------------
$net_dir = '//goose/test_share/';
$net_file = $net_dir."test.txt";
if (is_dir($net_dir)) {
    echo "  is_dir successful.\n";
} else {
    echo "  is_dir failed.\n";
}
if ($dh = opendir($net_dir)) {
    echo "  opendir successfull.\n";
} else {
    echo "  opendir failed.\n";
}



Expected result:
----------------
  is_dir successfull.
  opendir successfull.


Actual result:
--------------
  is_dir failed.
  opendir successfull.