Revert "Enable a couple of tests that were disabled because they"

tests/standalone/io/regress-6521.dart

Index: tests/standalone/io/regress-6521.dart
diff --git a/tests/standalone/io/regress_6521_test.dart b/tests/standalone/io/regress-6521.dart
similarity index 96%
rename from tests/standalone/io/regress_6521_test.dart
rename to tests/standalone/io/regress-6521.dart
index 9d393b703d01c62e1c4a4e625d2100173e8af9d6..a02025d2cb74ad103b4f4440d687cc7b66adf021 100644
--- a/tests/standalone/io/regress_6521_test.dart
+++ b/tests/standalone/io/regress-6521.dart
@@ -18,6 +18,10 @@ void main() {
       req.inputStream.read();
       rsp.outputStream.close();
     };
+    req.inputStream.onClosed = () {
+      client.shutdown();
+      server.close();
+    };
   };
 
   var connection = client.openUrl(
@@ -32,8 +36,6 @@ void main() {
     response.inputStream.onClosed = () {
       // Wait with closing the client request until the response is done.
       clientRequest.outputStream.close();
-      client.shutdown();
-      server.close();
     };
   };
 }