Addressed more intermittently failing specs.

Author: jdantonio

lib/concurrent/timer_task.rb

@@ -195,7 +195,7 @@ def initialize(opts = {}, &task)
       @executor = Concurrent::SafeTaskExecutor.new(task)
       @running = Concurrent::AtomicBoolean.new(false)
 
-      self.observers = CopyOnWriteObserverSet.new
+      self.observers = CopyOnNotifyObserverSet.new
     end
 
     # Is the executor running?

spec/concurrent/executor/per_thread_executor_spec.rb

@@ -7,10 +7,6 @@ module Concurrent
 
     subject { PerThreadExecutor.new }
 
-    after(:all) do
-      Concurrent.configuration.global_task_pool = PerThreadExecutor.new
-    end
-
     it_should_behave_like :global_thread_pool
 
     context '#post' do

spec/concurrent/timer_task_spec.rb

@@ -1,7 +1,6 @@
 require 'spec_helper'
 require_relative 'dereferenceable_shared'
 require_relative 'runnable_shared'
-#require_relative 'stoppable_shared'
 
 module Concurrent