rewinddir doesn't work, causing glibc tests to fail under disorderfs

This bug was originally reported by Ximin Luo (infinity0@debian.org) in Debian bug #844524:

See the attached test program. You should see something like this:

/tmp/debrepro.LJec0mD2n2/first/disorderfs$ gcc test.c && ./a.out; ls -lad tst-dir* && rmdir tst-dir*
haven't found new directory "/tmp/debrepro.LJec0mD2n2/first/disorderfs/tst-dir.L9Wbsn"
drwx------ 2 infinity0 infinity0 4096 Nov 16 14:37 tst-dir.L9Wbsn

/tmp/debrepro.LJec0mD2n2/first/disorderfs$ cp test.c ..
/tmp/debrepro.LJec0mD2n2/first/disorderfs$ cd ..
/tmp/debrepro.LJec0mD2n2/first$ gcc test.c && ./a.out && ls -lad tst-dir* && rmdir tst-dir*
drwx------ 2 infinity0 infinity0 4096 Nov 16 14:35 tst-dir.vpiYtA