[API] Fixed the Ruby 1.8-incompatible syntax in the "Nodes Info" API

Author: karmi

elasticsearch-api/test/unit/nodes/info_test.rb

@@ -66,7 +66,7 @@ class NodesInfoTest < ::Test::Unit::TestCase
             true
           end.returns(FakeResponse.new)
 
-          subject.nodes.info metric: ['http', 'network']
+          subject.nodes.info :metric => ['http', 'network']
         end
       end