Make Orchestra specs run on isolation.

activesupport/lib/active_support/orchestra.rb

 require 'thread'
 require 'active_support/core_ext/module/delegation'
+require 'active_support/core_ext/module/attribute_accessors'
 
 module ActiveSupport
   # Orchestra provides an instrumentation API for Ruby. To instrument an action

railties/test/application/orchestra_test.rb

 require "isolation/abstract_unit"
-require "active_support/orchestra"
 
 module ApplicationTests
   class OrchestraTest < Test::Unit::TestCase
+    include ActiveSupport::Testing::Isolation
 
     class MyQueue
       attr_reader :events, :subscribers
@@ -25,6 +25,7 @@ def setup
       build_app
       boot_rails
 
+      require "active_support/orchestra"
       Rails::Initializer.run do |c|
         c.orchestra.queue = MyQueue.new
         c.orchestra.subscribe(/listening/) do