Update 'last seen' field on flow rules

Change-Id: I7400bd181c41e605c03a60d05b08337e529e080a
diff --git a/core/store/dist/src/main/java/org/onosproject/store/flow/impl/NewDistributedFlowRuleStore.java b/core/store/dist/src/main/java/org/onosproject/store/flow/impl/NewDistributedFlowRuleStore.java
index dc1bf86..cc2f730 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/flow/impl/NewDistributedFlowRuleStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/flow/impl/NewDistributedFlowRuleStore.java
@@ -545,6 +545,7 @@
             stored.setBytes(rule.bytes());
             stored.setLife(rule.life());
             stored.setPackets(rule.packets());
+            stored.setLastSeen();
             if (stored.state() == FlowEntryState.PENDING_ADD) {
                 stored.setState(FlowEntryState.ADDED);
                 return new FlowRuleEvent(Type.RULE_ADDED, rule);