Add a configuration option to vary how heavyweight anti-entropy is.

Change-Id: I57cea61182b3d19deb47608ffb7dd617529ae34c

@@ -98,6 +98,7 @@ public class EventuallyConsistentMapImpl<K, V>
     // TODO: Make these anti-entropy params configurable
     private long initialDelaySec = 5;
     private long periodSec = 5;
+    private boolean lightweightAntiEntropy = true;
 
     /**
      * Creates a new eventually consistent map shared amongst multiple instances.
@@ -567,24 +568,18 @@ public class EventuallyConsistentMapImpl<K, V>
 
     private void handleAntiEntropyAdvertisement(AntiEntropyAdvertisement<K> ad) {
         List<EventuallyConsistentMapEvent<K, V>> externalEvents;
-        boolean sync = false;
 
         externalEvents = antiEntropyCheckLocalItems(ad);
 
         antiEntropyCheckLocalRemoved(ad);
 
+        if (!lightweightAntiEntropy) {
             externalEvents.addAll(antiEntropyCheckRemoteRemoved(ad));
 
             // if remote ad has something unknown, actively sync
             for (K key : ad.timestamps().keySet()) {
                 if (!items.containsKey(key)) {
-                sync = true;
-                break;
-            }
-        }
-
                     // Send the advertisement back if this peer is out-of-sync
-        if (sync) {
                     final NodeId sender = ad.sender();
                     AntiEntropyAdvertisement<K> myAd = createAdvertisement();
                     try {
@@ -594,8 +589,11 @@ public class EventuallyConsistentMapImpl<K, V>
                                 "Failed to send reactive anti-entropy advertisement to {}",
                                 sender);
                     }
-        }
 
+                    break;
+                }
+            }
+        }
         externalEvents.forEach(this::notifyListeners);
     }