[dir] fix potential memory leak in TDirectoryFile::mkdir()
[dir] fix potential memory leak in TDirectoryFile::mkdir()

Use TString to keep temporary subdirectory name
root-mirror/root,root-mirror/root,olifre/root,olifre/root,karies/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,karies/root,karies/root,karies/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,root-mirror/root,olifre/root,karies/root,root-mirror/root,karies/root,karies/root,root-mirror/root,root-mirror/root,olifre/root,karies/root,karies/root