ntdll: Fix NtQueryDirectoryFile behavior on short file names on case insensitive file systems

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
https://testbot.winehq.org/JobDetails.pl?Key=19069

Your paranoid android.


=== w1064 (32 bit directory) ===
directory.c:302: Test failed: incorrect long file name: L"longfilename.tmp\7434,"