When RARP is being shutdown, it pipes result of the shutdown of transport to self.

remote's shutdown is using `ask` pattern, so it can produce `Status.Failure`, which is not handled in RARP's state `WaitTransportShutdown`.
For fixing it added matching for `Status.Failure` and changed `RemoteTransport`'s shutdown signature to use `akka.Done`, which looks more consistent with other shutdown's and `akka.Done` is more verbose than previously used `Unit`.

akka-remote/src/main/scala/akka/remote/RemoteActorRefProvider.scala

@@ -4,6 +4,7 @@
 
 package akka.remote
 
+import akka.Done
 import akka.actor._
 import akka.dispatch.sysmsg._
 import akka.event.{ Logging, LoggingAdapter, EventStream }
@@ -59,10 +60,15 @@ private[akka] object RemoteActorRefProvider {
     }
 
     when(WaitTransportShutdown) {
-      case Event((), _) ⇒
+      case Event(Done, _) ⇒
         log.info("Remoting shut down.")
         systemGuardian ! TerminationHookDone
         stop()
+
+      case Event(Status.Failure(ex), _) ⇒
+        log.error(ex, "Remoting shut down with error")
+        systemGuardian ! TerminationHookDone
+        stop()
     }
 
   }