Rack::Test update: Rename response header -> headers

Author: jochenehret

spec/unit/controllers/internal/download_droplets_controller_spec.rb

@@ -64,7 +64,7 @@ def upload_droplet
           get "/internal/v2/droplets/#{process.guid}/#{process.droplet_checksum}/download"
 
           expect(last_response).to be_redirect
-          expect(last_response.header['Location']).to eq(expected_redirect)
+          expect(last_response.headers['Location']).to eq(expected_redirect)
         end
       end
 
@@ -250,7 +250,7 @@ def upload_droplet(target_droplet=droplet)
           get "/internal/v4/droplets/#{process.guid}/#{process.droplet_checksum}/download"
 
           expect(last_response).to be_redirect
-          expect(last_response.header['Location']).to eq('http://example.com/somewhere/else')
+          expect(last_response.headers['Location']).to eq('http://example.com/somewhere/else')
         end
 
         context 'when using with a revision' do
@@ -271,7 +271,7 @@ def upload_droplet(target_droplet=droplet)
             get "/internal/v4/droplets/#{process.guid}/#{new_droplet.checksum}/download"
 
             expect(last_response).to be_redirect
-            expect(last_response.header['Location']).to eq('http://example.com/correct/droplet')
+            expect(last_response.headers['Location']).to eq('http://example.com/correct/droplet')
           end
         end
       end

spec/unit/controllers/runtime/apps_controller_spec.rb

@@ -1818,7 +1818,7 @@ def delete_app
       it 'lets the user download the droplet' do
         get "/v2/apps/#{process.app.guid}/droplet/download", Oj.dump({})
         expect(last_response).to be_redirect
-        expect(last_response.header['Location']).to eq('http://example.com/somewhere/else')
+        expect(last_response.headers['Location']).to eq('http://example.com/somewhere/else')
       end
 
       it 'returns an error for non-existent apps' do

spec/unit/controllers/runtime/buildpack_bits_controller_spec.rb

@@ -316,7 +316,7 @@ module VCAP::CloudController
           authorize(staging_user, staging_password)
           get "/v2/buildpacks/#{test_buildpack.guid}/download"
           expect(last_response.status).to eq(302)
-          expect(last_response.header['Location']).to match(/cc-buildpacks/)
+          expect(last_response.headers['Location']).to match(/cc-buildpacks/)
         end
 
         it 'returns 404 for missing bits' do