Fix sticky bit directory handling for deletions.

Fix sticky bit directory handling for deletions.

Properly check the sticky bit and disallow deletions if set on a directory
and the user doing the deletion does not own the directory or the file.

This check is now being done by the kernel layer, VFSs do not need to do
this check any more.

Reported-by: YONETANI Tomokazu <qhwt+dfly@les.ath.cx>