Attribute for depsolver_timeout not used anywhere

The chef-server attributes includes `despsolver_timeout` but that value wasn't applied anywhere. Changed that value to match the
hard-coded value, 2000, at

https://github.com/opscode/chef_objects/blob/master/src/chef_depsolver.erl#L46

and updated erchef.config to use that value per

 https://github.com/opscode/chef_objects/blob/master/src/chef_depsolver.erl#L127