Yelp doesn't like OMFs installed in non-default prefixes. In the test system,
the prefix for yelp is /usr. The application is installed under /usr/local,
hence its omf is located in /usr/local/share/omf/foo. The omf file has been
registered with scrollkeeper-install (and the installation verified by grepping
the /var/lib/scrollkeeper files). However, yelp seems to completely ignore the
scrollkeeper index and looks for OMF files on its own. 

The installed documentation doesn't show up in the yelp browser in the category
specified. Running yelp under strace shows that it's looking for directories
under /usr/share/omf. Even symlinking /usr/local/share/omf/foo into
/usr/share/omf/foo and registering the doc doesn't work. yelp is looking for an
actual filesystem directory and won't accept the symlink.

As a result of this, unless the app is installed in the same prefix as yelp
(i.e. /usr), yelp doesn't pick up the OMF entry.