Wait on shutdown of extra actor systems in tests. See #3217

akka-docs/rst/scala/code/docs/testkit/PlainWordSpec.scala

@@ -31,7 +31,7 @@ class MySpec(_system: ActorSystem) extends TestKit(_system) with ImplicitSender
   import MySpec._
 
   override def afterAll {
-    system.shutdown()
+    TestKit.shutdownActorSystem(system)
   }
 
   "An Echo actor" must {

akka-docs/rst/scala/code/docs/testkit/TestKitUsageSpec.scala

@@ -45,7 +45,7 @@ class TestKitUsageSpec
     system.actorOf(Props(classOf[SequencingActor], testActor, headList, tailList))
 
   override def afterAll {
-    system.shutdown()
+    shutdown(system)
   }
 
   "An EchoActor" should {

akka-docs/rst/scala/code/docs/testkit/TestkitDocSpec.scala

@@ -264,7 +264,7 @@ class TestkitDocSpec extends AkkaSpec with DefaultTimeout with ImplicitSender {
         actor ! Kill
       }
     } finally {
-      system.shutdown()
+      shutdown(system)
     }
     //#event-filter
   }
@@ -282,7 +282,7 @@ class TestkitDocSpec extends AkkaSpec with DefaultTimeout with ImplicitSender {
       try expectMsg("hello") catch { case NonFatal(e) ⇒ system.shutdown(); throw e }
       //#put-your-test-code-here
 
-      system.shutdown()
+      shutdown(system)
     }
     //#test-kit-base
   }