Corrected OOO with sensu needing rabbit

We have meta configs in some roles to run common, rabbit, and
sensu-client.  However, common and sensu-client are already
applied to every node.  Having the extra dependencies in each
role IMO, convoluted tasks.  Maybe I am wrong.  Maybe it is
better to add dependencies inside the role, however, it looks
clearer in the main site.yml.  Also, made sure rabbit is installed
first.