Don't clear cache when adding feature from factory

Author: benaadams

src/Microsoft.AspNet.Http.Features/FeatureReferences.cs

@@ -37,18 +37,15 @@ public TFeature Fetch<TFeature, TState>(
             }
 
             var feature = cached;
-            if (feature == null)
+            if (feature == null || cleared)
             {
                 feature = Collection.Get<TFeature>();
                 if (feature == null)
                 {
                     feature = factory(state);
 
                     Collection.Set(feature);
-                    if (!cleared)
-                    {
-                        Cache = default(TCache);
-                    }
+
                     Revision = Collection.Revision;
                 }
                 cached = feature;
@@ -59,4 +56,4 @@ public TFeature Fetch<TFeature, TState>(
         public TFeature Fetch<TFeature>(ref TFeature cached, Func<IFeatureCollection, TFeature> factory) =>
             Fetch(ref cached, Collection, factory);
     }
-}
+}