Move persist tracking context out of the loop in AbstractFlushingEventListener (#3310)

Fixes #3307

Author: hazzik

src/NHibernate/Async/Event/Default/AbstractFlushingEventListener.cs

@@ -191,6 +191,7 @@ protected virtual async Task PrepareEntityFlushesAsync(IEventSource session, Can
 			cancellationToken.ThrowIfCancellationRequested();
 			log.Debug("processing flush-time cascades");
 
+			var anything = Anything;
 			ICollection list = IdentityMap.ConcurrentEntries(session.PersistenceContext.EntityEntries);
 			//safe from concurrent modification because of how entryList() is implemented on IdentityMap
 			foreach (DictionaryEntry me in list)
@@ -199,7 +200,7 @@ protected virtual async Task PrepareEntityFlushesAsync(IEventSource session, Can
 				Status status = entry.Status;
 				if (status == Status.Loaded || status == Status.Saving || status == Status.ReadOnly)
 				{
-					await (CascadeOnFlushAsync(session, entry.Persister, me.Key, Anything, cancellationToken)).ConfigureAwait(false);
+					await (CascadeOnFlushAsync(session, entry.Persister, me.Key, anything, cancellationToken)).ConfigureAwait(false);
 				}
 			}
 		}

src/NHibernate/Event/Default/AbstractFlushingEventListener.cs

@@ -188,6 +188,7 @@ protected virtual void PrepareEntityFlushes(IEventSource session)
 		{
 			log.Debug("processing flush-time cascades");
 
+			var anything = Anything;
 			ICollection list = IdentityMap.ConcurrentEntries(session.PersistenceContext.EntityEntries);
 			//safe from concurrent modification because of how entryList() is implemented on IdentityMap
 			foreach (DictionaryEntry me in list)
@@ -196,7 +197,7 @@ protected virtual void PrepareEntityFlushes(IEventSource session)
 				Status status = entry.Status;
 				if (status == Status.Loaded || status == Status.Saving || status == Status.ReadOnly)
 				{
-					CascadeOnFlush(session, entry.Persister, me.Key, Anything);
+					CascadeOnFlush(session, entry.Persister, me.Key, anything);
 				}
 			}
 		}