The latest import for the Dockerfile began having failures due to apache
configuration changes in debian. This update fixes those failures and
pins the base debian image to avoid these issues until we need to update
debian itself.
* net_smtp2 to net_smtp
* auth_sasl2-beta to auth_sasl
Currently installing `Net_SMTP2` results with the following error:
```bash
[09-Jan-2015 21:15:14 UTC] PHP Fatal error: Class 'Net_SMTP' not found in /var/www/program/lib/Roundcube/rcube_smtp.php on line 111
```
Switching back to Net_SMTP fixes this issue
prashant