templates: postfix: set same timeouts for before and after-queue

templates: postfix: set same timeouts for before and after-queue

When a mail takes longer to get processed (observed with some scanned
pages as pdf - where clamav+avast took 2.2 minutes for scanning) the
behavior of the filtering is different between before-queue and
after-queue filtering:
In the before-queue case the timeout is `$smtpd_proxy_timout` (120s)
[0], so the mail does not get processed in time and the listening
smtpd responds with `451 4.3.0 Error: queue file write error`. However
pmg-smtp-filter sends the mail to the smtpd on 10025 once it's done.
the original sender resends the mail due to the 451 error - which
results in the mail getting delivered multiple times (until it gets
removed from the queue on the original sender)

In the after-queue case the timeout is `$lmtp_data_done_timeout`
(pmg-smtp-filter acts as lmtp server) (600s) - so the mail gets
send successfully only once. In case the processing time reaches
600s the behavior is equivalent - but for lmtp postfix logs:
```
...timed out while sending end of data -- message may be sent more
than once
```

The value needs to be set as literal - referring to the builtin
default as `$lmtp_data_done_timeout` does not work.

While the underlying issue of mails getting sent multiple times in
case the timeout is reached is not fixed by this - having the same
timeout in both cases is a good idea and 600s increases the chances
of clamav+avast+custom_check_script+spamassassin to get their job done.

tested by adding a `sleep 200` in PMG::Utils::analyze_virus_clam.
(before the eval block running with the 5 minute timeout)

[0] https://www.postfix.org/SMTPD_PROXY_README.html#parameters

Reported-by: Martin Maurer <martin@proxmox.com>
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>