Make reset conditional based on state.

Author: benaadams

src/Microsoft.AspNet.Server.Kestrel/Http/Frame.cs

@@ -200,9 +200,12 @@ public bool HasResponseStarted
             get { return _responseStarted; }
         }
 
-        public void Reset()
+        public bool Reset()
         {
-            TransitionToState(FrameState.Waiting);
+            if (TransitionToState(FrameState.Waiting) != FrameState.Waiting)
+            {
+                return false;
+            }
 
             _onStarting = null;
             _onCompleted = null;
@@ -251,6 +254,8 @@ public void Reset()
 
             _manuallySetRequestAbortToken = null;
             _abortedCts = null;
+
+            return true;
         }
 
         public void ResetResponseHeaders()

src/Microsoft.AspNet.Server.Kestrel/Http/FrameOfT.cs

@@ -135,7 +135,10 @@ public override async Task RequestProcessingAsync()
                         }
                     }
 
-                    Reset();
+                    if (!Reset())
+                    {
+                        return;
+                    }
                 }
             }
             catch (Exception ex)