RFR: 8068384: Memleak in WinNTFileSystem_md.c

[Ivan Gerasimov]

Hello!

There appears to be a memory leak in WinNTFileSystem_list() function.
I should have noticed it when doing cleanup with JDK-8056310, but missed 
it somehow.

Would you please help review the fix?

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8068384
WEBREV: http://cr.openjdk.java.net/~igerasim/8068384/0/webrev/

Sincerely yours,
Ivan