[dm-crypt] luksAddKey one liner

Let's say you create a new volume as follows:

    echo -n pass0 | cryptsetup luksFormat /dev/sda2 -

So the password in keyslot #0 is "pass0".

Next, you want to set the password in keyslot #1 to "pass1", well I figured out how to do it with a one-liner:

    echo -n "pass0pass1" | cryptsetup luksAddKey --key-file /dev/stdin --keyfile-size 5 --key-slot 1 /dev/sda2 /dev/stdin
 
Frederick