Code review comment for ~paul-meyer/cloud-init:fix-raw-ephemeral-disk

Hey, thanks for your patience.
I'm going to pull this.that module can definitely use some cleanup.
curtin has lots of stuff that does this sort of thing better.

For something like "find out how big a block device is" in sectors we could do something like:

$ sudo blockdev --getsize /dev/sdb
83886080

$ cat /sys/class/block/sdb/size
83886080

For that value in bytes:
 $ sudo blockdev --getsize64 /dev/sdb
42949672960