Cache version list results even when they fail.

sdk/lib/_internal/pub/test/hosted/version_negotiation_test.dart

Index: sdk/lib/_internal/pub/test/hosted/version_negotiation_test.dart
diff --git a/sdk/lib/_internal/pub/test/hosted/version_negotiation_test.dart b/sdk/lib/_internal/pub/test/hosted/version_negotiation_test.dart
index 76018d9f29f6b268a4f844cd2cd586a4f5323ac0..f6026186ab45b7da243a69ed71315886f8942fe7 100644
--- a/sdk/lib/_internal/pub/test/hosted/version_negotiation_test.dart
+++ b/sdk/lib/_internal/pub/test/hosted/version_negotiation_test.dart
@@ -55,10 +55,6 @@ main() {
       server.handle('GET', '/api/packages/foo',
           (request) => new shelf.Response(406));
 
-      // TODO(nweiz): this shouldn't request the versions twice (issue 11077).
-      server.handle('GET', '/api/packages/foo',
-          (request) => new shelf.Response(406));
-
       pub.shouldExit(1);
 
       pub.stderr.expect(emitsLines(