Clean up observatory testing processes when we are done with them.

runtime/bin/vmservice/vmservice_io.dart

Index: runtime/bin/vmservice/vmservice_io.dart
diff --git a/runtime/bin/vmservice/vmservice_io.dart b/runtime/bin/vmservice/vmservice_io.dart
index 070a25c3dc62aa963153abcd6f9e864a5bfdab2d..4896b218c5b53a7bc9447c80fd5885afc32eaa2e 100644
--- a/runtime/bin/vmservice/vmservice_io.dart
+++ b/runtime/bin/vmservice/vmservice_io.dart
@@ -31,7 +31,9 @@ Future<Server> serverFuture;
 
 _onShutdown() {
   if (server != null) {
-    server.close(true).catchError((e, st) => assert(e));
+    server.close(true).catchError((e, st) {
+      print("Error in vm-service: $e\n$st\nExiting...");

[Ivan Posva, 2015/03/27 07:51:36]

How about "Error in vm-service shutdown"? To make clear in which phase this
message was generated.

[turnidge, 2015/03/27 16:01:37]

Done.

+    });
   }
   if (_signalSubscription != null) {
     _signalSubscription.cancel();