Fixing setup-storage_no-cylinder-boundaries

[Julien BLACHE]

Hi,

setup-storage_no-cylinder-boundaries in experimental had serious issues
with preserving msdos partitions created by previous versions of
setup-storage.

There were 2 issues:
 - aligning to sector boundary instead of cylinder boundary by default
 - aligning the start position of partitions 1 and 5

This leads to the new setup-storage creating partitions that are up to
several megabytes larger than they were with the old setup-storage.

I've fixed both issues by:
 - reverting to cylinder boundary for msdos partitions by default, but
   align-at can override that
 - ignoring alignment constraints for the start of partitions 1 and 5 on
   msdos disk labels

Basically, we shouldn't mess with alignment on msdos disklabels, it's
going to break backward compatibility.

JB.

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 Julien BLACHE - Debian & GNU/Linux Developer - <jblache at debian.org> 
 
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