In cases where the whole EXIF MakerNote is invalid we still load that
MakerNote data and export it too, causing partial invalid EXIF metadata.
We don't need to explicitly save Exif.Photo.MakerNote at all, because
as soon as we try to save a brand specific tag exiv2 will create that
MakerNote tag itself.
So from now we don't save the MakerNote but only the tags that go in it.
In issues like #2159 where exiv2 doesn't parse all tags inside certain
brand specific MakerNotes correctly, we will still export invalid EXIF.
That is an exiv2 issue that we can't do much about unless we remove all
MakerNote metadata including those that we can read, which doesn't seem
like a good idea at all.
(cherry picked from commit 6840bb9eba)
57f20f6fac