Ignore duplicate deletes in FlowStatsCollector module.

In some transient cases it is possible that two flows with same flow Key
exists in two different partitions. In this scenario, FlowStatsCollector module
can receive duplicate deletes. For now, the FlowStatsCollector module will ignore
duplicate deletes and this scenario will be handled later in FlowStatsCollector by
changing the key from FlowKey to FlowUUID.

Also print partition-id in Flow trace messages.

Change-Id: I79988347a2c7294215e63e950ef871e25a126b3c
Closes-Bug: #1543411

src/vnsw/agent/pkt/flow_entry.cc

@@ -1867,6 +1867,9 @@ void FlowEntry::FillFlowInfo(FlowInfo &info) {
     info.set_smac(data_.smac.ToString());
     info.set_dmac(data_.dmac.ToString());
     info.set_drop_reason(FlowEntry::DropReasonStr(data_.drop_reason));
+    if (flow_table_) {
+        info.set_table_id(flow_table_->table_index());
+    }
 }
 
 static void SetAclListAceId(const AclDBEntry *acl,

src/vnsw/agent/pkt/pkt.sandesh

@@ -239,6 +239,7 @@ struct FlowInfo {
    37: optional u64 dip_upper;
    38: optional u64 dip_lower;
    43: string drop_reason;
+   44: u16 table_id;
 }
 
 /**

src/vnsw/agent/vrouter/flow_stats/flow_stats_collector.cc

@@ -800,8 +800,12 @@ bool FlowStatsCollector::RequestHandler(boost::shared_ptr<FlowExportReq> req) {
         /* Fetch the update stats and export the flow with teardown_time */
         FlowExportInfo *info = FindFlowExportInfo(req->key());
         if (!info) {
-            /* Do not expect duplicate deletes */
-            assert(0);
+            /* Ignore duplicate deletes for NOW. When two flow-entries point
+             * to same flow-key (because entries are in different partition),
+             * we can get duplicate deletes */
+            /* TODO: change the flow_tree_ key of FlowStatsCollector from
+             * FlowKey to Flow UUID */
+            break;
         }
         /* While updating stats for evicted flows, we set the teardown_time
          * and export the flow. So delete handling for evicted flows need not