Bug#768577: Patch applied upstream

[Quentin Lefebvre]

So here is the point of view of the developers.
The upstream patch works provided that "hash=plain" is mentioned in 
/etc/cryptab.

To summarize:
- when a user creates a plain dm-crypt device providing a --hash 
parameter along with a key file
- he *should* be aware of the fact that the hash parameter is ignored
- and as a consequence, he should write "hash=plain" in /etc/crypttab
- in short, it's a cryptsetup bug, and systemd won't be "compatible with 
cryptsetup's bug"...

Let's say that's fine. It may be worth documenting this.

Please note that this patch basically changes nothing about the 
aforementioned bug, so I'm not convinced it should be applied in Debian, 
and I don't attach it.
The trick with "hash=plain" already works with Debian's current version 
of systemd.

Best regards,
Quentin