This is what I had to do on my EL5 box to get 2.2.1 working after updating
from 2.0.11:

- Modify the /etc/cobbler/modules.conf.rpmnew file to have my modified
settings and move into place.  cobblerd would start without the new [tftpd]
configuration settings
- Move the /etc/httpd/conf.d/cobbler_web.conf.rpmnew file into place, and
comment out the VirtualHost lines so that I could access via https.
- Remove mod_python
- Uncomment the LoadModule command in /etc/httpd/conf.d/wsgi.conf
- Change $kickstart_start/_done to $SNIPPET('kickstart_start')/_done in my
default kickstart template.
- Had to move a section of one of my snippets into a #raw/#end raw block so
some as yet undetermined reason - probably new cheetah commands

Also, koan 2.2.1 appears to need to talk to the cobbler xmlrpc port directly
now rather than going through the web interface?  But cobblerd is only
listening on localhost so remote koan connections fail.  Not sure what to do here.