Bug#393913: suggested fix wrong for apache2: After an upgrade index.php wouldn't load automatically
The author is correct that the line is missing, but the problem is that
the line was moved to mod_dir.conf, which is a NEW file in 2.2, but
wasn't symlinked into mods-enabled.
We're doing upgrading incorrectly in general. I'm wondering if the
"proper" way to do it is to look at the existing active modules list and
do a "a2dismod <module> && a2enmod <module>" to bring over any new files?
That has its own potential issues, but in this particular case, the real
bug is that mod_dir.conf didn't get symlinked in.