Fix truncation point

[morpheusthewhite]

Launching cannolo.sh on a previously shrinked image causes the script to fail: a parted command exits with error

Error: Can't have a partition outside the disk!

When comparing the size of the partition (parted in interactive mode) with the phisical size of the file it appears the file is truncated before the end, even if the both of them parted and truncate rely on the same variable.

Nonetheless the shrinked image works.