The manage command for rb-site is in the wrong spot in the cron.  Moving the order to before the site path fixes the cron to work properly.

[root@dev01 conf]# cat /etc/cron.d/search-cron.conf 
# Incremental indices every 10 minutes
0,10,20,30,40,50 * * * * /usr/local/bin/rb-site manage /var/www/reviewboard index

# Do a full index once a week on Sunday at 2am
* 2 * * 0 /usr/local/bin/rb-site manage /var/www/reviewboard index -- --full

[root@dev01 conf]# /usr/local/bin/rb-site manage /var/www/reviewboard index
Creating Review Request Index
Optimizing Index
Indexed 0 documents
Done