Cannot find a resource for preferred_state

This resolves an issue that has crept in with opscode php cookbook.

There is a pull request in place to that project: https://github.com/opscode-cookbooks/php/pull/54

I am not referencing the project which is the source of the above pull request because it is a little bit behind. But instead I have merged their changes in an elifesciences project: https://github.com/elifesciences/chef-opscode-php

This will be redundant once the above pull request is accepted.