Extended boot records (EBRs) are used in the MSDOS partitioning
scheme to manage extended partitions. EBRs are small partitions
themselves and Ironic will therefore treat them like any other
partition during cleaning. Since EBRs are smaller than a GPT
(33 sectors), dd'ing 33 sectors will fail. This patch proposes
a fix to handle EBRs (and other tiny paritions) by adjusting
the number of blocks writtent to be the partition size at max.
(cherry picked from commit