Handle split redis/api/rabbit hosts, hosted redis.

[jhmartin]

The rabbit/redis/api servers may be on different hosts (and perhaps not even search()able in the case of AWS hosted redis). It would be useful if the search blocks could be separated and also overrideable by a static value.

[rodriguezsergio]

Use node.force_override in a wrapper cookbook to get around this issue. That's what I'm doing for my rabbitMQ cluster and it works fine. The force_override precedence is higher than override, so node.override["sensu"]["redis"]["host"] = master_address doesn't supersede your custom value.

[portertech]

This cookbook is an example wrapper cookbook for Sensu, most users must fork it in order to use it. I'm open to a pull-request that improves the user experience for this deployment method/configuration.