Fix for Chef::Exceptions::ValidationFailed for cookbook (passenger_apache2 provider)

Chef 10.12 and ruby 1.9.3

Force cookbook to be a string.

    application "app_name_com" do
      ...
      passenger_apache2 do
      end
    end

This would cause the following error.

[2012-09-08T18:14:14+00:00] FATAL: Chef::Exceptions::ValidationFailed: ruby_block[app_name_com before_deploy] (/tmp/vagrant-chef-1/chef-solo-1/cookbooks/application/providers/default.rb line 107) had an error: Chef::Exceptions::ValidationFailed: application_ruby_passenger_apache2[app_name_com] (qudos_com::default line 109) had an error: Chef::Exceptions::ValidationFailed: Option cookbook must be a kind of [String]!  You passed :app_name_com.

This fix is simple to force the proper behavior.