[COOK 4001] only create /etc/init/mysql.conf on the ubuntu platform

The template - `init-mysql.conf.erb` - does not exist in the templates directory for debian, and therefore this fails to install on debian systems. The mysql package provides an init file, so it is not necessary for those systems.
[COOK 3931] Move ubuntu-12 init-mysql.conf.erb template to default specificity

The template is required on ubuntu systems and need only be overriden by ubuntu-10. Thus, it makes most sense to move it to default specificity, rather than override for each ubuntu version forever.

Refs:

- COOK-3931
- COOK-3945
- COOK-3966
- COOK-3974
- COOK-3985
- COOK-4001
- COOK-4071

PRs:

- opscode-cookbooks/mysql#128
- opscode-cookbooks/mysql#132
- opscode-cookbooks/mysql#137
- opscode-cookbooks/mysql#144
- opscode-cookbooks/mysql#146

Affected systems:

- Non-LTS Ubuntu
- Debian-based systems
Run specs on Ubuntu 13.04