Resolve test name conflict

In AfterFilterTest in filter_test.rb there are two tests named
"executes filters in the order defined", causing the first not to be
run.

Rename the first test, and fix the mock app in the test so it doesn't
cause a Rack::Lint error.

test/filter_test.rb

@@ -156,11 +156,11 @@ class BeforeFilterTest < Test::Unit::TestCase
 end
 
 class AfterFilterTest < Test::Unit::TestCase
-  it "executes filters in the order defined" do
+  it "executes before and after filters in correct order" do
     invoked = 0
     mock_app do
       before   { invoked = 2 }
-      get('/') { invoked += 2 }
+      get('/') { invoked += 2; 'hello' }
       after    { invoked *= 2 }
     end