Update coriolis-writer build

The repo contains a build of "coriolis-writer", which recently
received new features:

* v2 api, allowing devices to be identified by SCSI ID/address
    * more reliable than device names such as /dev/sdb
    * no longer need to attach and identify the disks sequentially
      from the guest side, as long as the target platform can provide
      the SCSI ID or address
* asynchronous checksum API

That being said, we'll update the coriolis-writer binary.