Fix checks in can_delete_file_in_directory()

Fix checks in can_delete_file_in_directory()

With at least NFSv4 ACLs around the write permission for the owner is a bogus
check if we can delete a file in a directory. Like in Windows, there are two
ways which can grant us such: First, the DELETE permission on the file itself,
or if that does not help, the DELETE_CHILD permission on the directory. It
might be a bit more code that runs, but essentially we should end up with the
same set of syscalls in the non-acl case.