[CLIENT] Fix Curb unit test, expecting headers to be merged and not set

Author: estolfo

elasticsearch-transport/lib/elasticsearch/transport/transport/http/curb.rb

@@ -46,7 +46,7 @@ def perform_request(method, path, params={}, body=nil, headers=nil)
 
                   if headers
                     if connection.connection.headers
-                      connection.connection.headers.merge(headers)
+                      connection.connection.headers.merge!(headers)
                     else
                       connection.connection.headers = headers
                     end

elasticsearch-transport/test/unit/transport_curb_test.rb

@@ -57,7 +57,7 @@ class Elasticsearch::Transport::Transport::HTTP::FaradayTest < Minitest::Test
       should "perform request with headers" do
         @transport.connections.first.connection.expects(:put_data=).with('{"foo":"bar"}')
         @transport.connections.first.connection.expects(:http).with(:POST).returns(stub_everything)
-        @transport.connections.first.connection.expects(:headers=).with({"Content-Type" => "application/x-ndjson"})
+        @transport.connections.first.connection.headers.expects(:merge!).with("Content-Type" => "application/x-ndjson")
 
         @transport.perform_request 'POST', '/', {}, {:foo => 'bar'}, {"Content-Type" => "application/x-ndjson"}
       end