Utils: Update Attoparsec import

The module Data.Attoparsec is deprecated in attoparsec 0.12
and Data.Attoparsec.ByteString is the recommended replacement,
which is backwards compatible until attoparsec 0.10 (2011),
the oldest package available in the Debians.

Signed-off-by: Niklas Hambuechen <niklash@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>