Monkey patch ftw.mail.inbound.createMailInContainer because

`preserved_as_paper` has a schema level default, its default
value doesn't get set correctly, so we set explicitely after setting
the defaults.

(cherry picked from commit eb1ba9e8a06256ce4e992f8c413493d8da734a63)
Merge pull request #525 from 4teamwork/lg-backport-create-mail-in-container-monkeypatch

Backport `Monkey patch ftw.mail.inbound.createMailInContainer` to 3.4-stable