Bug 26705: (QA follow-up) Do not rely on latest Email::MIME

Bug 26705: (QA follow-up) Do not rely on latest Email::MIME

This patch makes the implementation use lower-level methods to deal with
headers. So the Email::MIME library in Debian 9 works.

Params are sorted for testing purposes.

To test:
1. Apply this patch
2. Run the tests
=> SUCCESS: Things pass in D9+
3. Sign off :-D

Thanks Kyle!

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>