Make "pub run foo" run "pub run foo:foo" rather than "pub run bin/foo"

sdk/lib/_internal/pub/test/run/passes_along_arguments_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 
 const SCRIPT = """
 main(List<String> args) {
   print(args.join(" "));
 }
 """;
 
 main() {
   initConfig();
   integration('passes arguments to the spawned script', () {
     d.dir(appPath, [
       d.appPubspec(),
       d.dir("bin", [
         d.file("args.dart", SCRIPT)
       ])
     ]).create();
 
     // Use some args that would trip up pub's arg parser to ensure that it
     // isn't trying to look at them.
-    var pub = pubRun(args: ["args", "--verbose", "-m", "--", "help"]);
+    var pub = pubRun(args: ["bin/args", "--verbose", "-m", "--", "help"]);
 
     pub.stdout.expect("--verbose -m -- help");
     pub.shouldExit();
   });
 }