Unit test: update oood configuration only if needed and without reindexing

This was breaking tests assuming there is no activity at the beginning, like in
testCMFActivity.

Also try to revert [33605] because default_site_preference should always exist
now.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@33624 20353a03-c40f-0410-a6d1-a30d3c3de9de