Update locate_config_file scope to reflect its change to a Class method

The locate_config_file was changed to a class method on 2013-10-09:
opscode/chef@2a214bc#diff-1220e994288a7f7d9ae83196ce7fad9eL317

* Fix scope, and add abbreviated assignment for config[:config_file]
* Add tests for two GreenAdnSecure Module methods
** Test 002 should catch any future upstream breakage

Refactor TestKnifeBlockList

* The ! in front of File.symlink? asserts true if knife.rb is not a
  symlink; which appeared opposite of the goal.
* Set @chef_path to fallback to ~/.chef if WORKSPACE not defined
  ** This could also be sourced from locate_config_file which
     checks in more locations: KNIFE_HOME, pwd, and HOME.