Change pub tests and pub local server to use ipV4 localhost by address.

sdk/lib/_internal/pub/test/test_pub.dart

Index: sdk/lib/_internal/pub/test/test_pub.dart
diff --git a/sdk/lib/_internal/pub/test/test_pub.dart b/sdk/lib/_internal/pub/test/test_pub.dart
index 897b69e92fce68bd28ef63ce42685b7d1dc8e0a1..1f79116a6b243943a247facf7d468e6de1bffee0 100644
--- a/sdk/lib/_internal/pub/test/test_pub.dart
+++ b/sdk/lib/_internal/pub/test/test_pub.dart
@@ -94,7 +94,7 @@ void serve([List<d.Descriptor> contents]) {
 
   schedule(() {
     return _closeServer().then((_) {
-      return SafeHttpServer.bind("localhost", 0).then((server) {
+      return SafeHttpServer.bind("127.0.0.1", 0).then((server) {
         _server = server;
         server.listen((request) {
           currentSchedule.heartbeat();
@@ -485,7 +485,7 @@ ScheduledProcess startPub({List args, Future<Uri> tokenEndpoint}) {
     // dependencies will look there.
     if (_hasServer) {
       return port.then((p) {
-        environment['PUB_HOSTED_URL'] = "http://localhost:$p";
+        environment['PUB_HOSTED_URL'] = "http://127.0.0.1:$p";
         return environment;
       });
     }