[RAILS] Fixed incorrectly mocked search response in instrumentation test

Failures on Ruby 1.2.1

Author: karmi

elasticsearch-rails/test/unit/instrumentation/instrumentation_test.rb

@@ -20,9 +20,8 @@ def self.document_type; 'bar'; end
 
     setup do
       @search   = Elasticsearch::Model::Searching::SearchRequest.new ::DummyInstrumentationModel, '*'
-      @response = Elasticsearch::Model::Response::Response.new ::DummyInstrumentationModel, @search
 
-      @client = stub('client', search: @response)
+      @client = stub('client', search: RESPONSE)
       DummyInstrumentationModel.stubs(:client).returns(@client)
 
       Elasticsearch::Rails::Instrumentation::Railtie.run_initializers