Comment 2 for bug 1542690

Hi,
in the log I found:
ERROR: Config file jk.conf not properly enabled: /etc/apache2/mods-enabled/jk.conf is a real file, not touching it
[...]
apache2_invoke jk: already enabled

This means you had /etc/apache2/mods-enabled/jk.conf lying around likely from libapache2-mod-jk.
But this only puts files in /etc/apache2/mods-available and would put a symlink into /etc/apache2/mods-enabled.
I'd expect a manual config change to these files broke the update.

As confirmation I took a precise image installed apache2/tomcat7 and mod-jk.
The file /etc/apache2/mods-enabled/jk.conf was there for me as well - but only a symlink as deployed by the package, then I did an upgrade to 14.04 - working fine regarding apache.

I hope this helps you to get your upgrade done - marking the bug as not-a-bug for now, please reopen if you think that does not apply.