[WIP] Support `Sensu` 0.14.0.

Somehow, the `sensu-custom` cookbook is broken.
This PR is intended to fix this issue.
Change the `Sensu`-related attributes.

- Remove unnecessary default attributes
- Specifically enable `Rabbitmq` ssl (due to the `Rabbitmq` cookbook behaviour change)
- Specify the `Rabbitmq` ssl certificates (due to the `Rabbitmq` cookbook behaviour change)
Allow poodle attack in `Rabbitmq` configuration in Ubuntu 12.04.

The Erlang that Ubuntu 12.04 installs does not apply the patch,
which solves the SSL poodle attack problem.
In order to workaround this issue in Ubuntu 12.04 environment,
add "ssl_allow_poodle_attack,  true" to the configuration file.
Add test for `ssl_allow_poodle_attack` in Ubuntu 12.04.
Merge pull request #137 from kazu634/sensu-0140-support

Support `Sensu` 0.14.0.