Code review comment for lp:~seb128/debian-cd/splash-for-canary

Just making sure, since this changes the KERNEL_PARAMS for the canary case a bit - we don't use the 'file=/cdrom/preseed/ubuntu.seed' cmdline for the canary images? Since previously it was still included as we were only prepending layerfs-path to an existing KERNEL_PARAMS, but now we don't. I don't know enough about canary to know if that's all okay