quarantine: use reinject_local_mail to deliver quarantined mail

quarantine: use reinject_local_mail to deliver quarantined mail

the current delivery looks quite similar to reinject_local_mail,
apart from the database handling and sending the mail-contents from a
file instead of a MIME::Entity.

reinject_mail has received a few improvments over time, which never
made it to this implementation - e.g. in:
* ebd31d3e74d9417375b86766ee300be493044d39
* ad1c6bcea94cbaf8d4862bcb05874b59c656c632

While reparsing the mail might seem expensive, the quarantine code
does so multiple times when users click in the quarantine GUI (see
PMG::HTMLMail, and the attachment quarantine)

The issue of MIME::Parser being lossy [0] (parsing and then printing
the entity, might not return the original mail byte-by-byte), is
already present in our code-base anyways (when the mail gets
quarantined (or sent on) it is from a parsed MIME::Entity).

[0] https://metacpan.org/pod/MIME::Tools

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Reviewed-by: Dominik Csapak <d.csapak@proxmox.com>
Tested-by:  Dominik Csapak <d.csapak@proxmox.com>