I can reproduce this error in Percise.  What's happening is that apache is being restarted a second time to soon.  I've included the postinst script output below.

To test the theory I ran 'invoke-rc.d apache2 restart;invoke-rc.d apache2 restart' - the second restart failed.  If I add a sleep 'invoke-rc.d apache2 restart; sleep 1; invoke-rc.d apache2 restart' then the second restart succeeds.

The postinst script could be changed so that it would only ever call restart once. 

Looks like there is already a bug files against apache https://bugs.launchpad.net/ubuntu/+source/apache2/+bug/1018171 



bash -x  /var/lib/dpkg/info/puppetmaster-passenger.postinst configure
+ set -e
+ '[' configure = configure ']'
+ dpkg-statoverride --list /usr/share/puppet/rack/puppetmasterd/config.ru
+ '[' '' = '' ']'
++ puppet config print hostcert
+ '[' '!' -e /var/lib/puppet/ssl/certs/example.com.pem ']'
++ puppet config print
++ wc -l
++ grep 'Could not parse'
+ '[' 0 '!=' 0 ']'
+ APACHE2_SITE_FILE=/etc/apache2/sites-available/puppetmaster
+ '[' '!' -e /etc/apache2/sites-available/puppetmaster ']'
+ a2enmod ssl
Module ssl already enabled
+ a2enmod headers
Module headers already enabled
+ a2ensite puppetmaster
Site puppetmaster already enabled
+ '[' -x /etc/init.d/apache2 ']'
++ which invoke-rc.d
+ '[' -x /usr/sbin/invoke-rc.d ']'
+ invoke-rc.d apache2 restart
 * Restarting web server apache2                                                                                                                 apache2: Could not reliably determine the server's fully qualified domain name, using example.com for ServerName
[Wed Jul 04 10:54:55 2012] [warn] NameVirtualHost *:80 has no VirtualHosts
 ... waiting apache2: Could not reliably determine the server's fully qualified domain name, using example.com for ServerName
[Wed Jul 04 10:54:56 2012] [warn] NameVirtualHost *:80 has no VirtualHosts
                                                                                                                                          [ OK ]
+ dpkg --compare-versions '' lt-nl 2.6.1-1
+ dpkg --compare-versions '' le 2.7.11-1
+ APACHE2_SITE_FILE=/etc/apache2/sites-available/puppetmaster
+ '[' -e /etc/apache2/sites-available/puppetmaster ']'
+ sed -r -i 's|/etc/puppet/rack|/usr/share/puppet/rack/puppetmasterd|' /etc/apache2/sites-available/puppetmaster
+ a2enmod headers
Module headers already enabled
+ '[' -x /etc/init.d/apache2 ']'
++ which invoke-rc.d
+ '[' -x /usr/sbin/invoke-rc.d ']'
+ invoke-rc.d apache2 restart
 * Restarting web server apache2                                                                                                                 apache2: Could not reliably determine the server's fully qualified domain name, using example.com for ServerName
[Wed Jul 04 10:54:57 2012] [warn] NameVirtualHost *:80 has no VirtualHosts
apache2: Could not reliably determine the server's fully qualified domain name, using example.com for ServerName
[Wed Jul 04 10:54:57 2012] [warn] NameVirtualHost *:80 has no VirtualHosts
(98)Address already in use: make_sock: could not bind to address 0.0.0.0:80
no listening sockets available, shutting down
Unable to open logs
                                                                                                                                          [fail]
invoke-rc.d: initscript apache2, action "restart" failed.
+ exit 1