[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-4001

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