Check detached signatures to ensure that we're attaching a valid PKCS7
object. If no, show a warning message and skip the attach action.
Signed-off-by: Ivan Hu <ivan.hu@canonical.com>
Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Rather than requiring an explicit image_pecoff_parse, do it
unconditionally in image_load. We don't have any instances where we need
to do this separately.
Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>