CHEF-3664 The 'map' variable is defined and never used in the set_or_return method of lib/chef/mixim/params_validate.rb

The internal 'map' variable is never used; for the sake of symmetry with the other argument passed to validate, I think 'map' should be removed altogether.

This pull request replaces https://github.com/opscode/chef/pull/518 : I thought pull requests were based on 'static' commits, hadn't realized they were based on branches instead.