fix ToR-agent crash for stale timer cb

Issue:
------
Stale entry timer triggered delete on a deleted entry
causing invalid state machine event, ideally when an
Add/Change/Delete event happens it should have removed
entry from the stale entry tree. however along with
last change for sync DB request from a workqueue this
removal of entry from the stale entry tree got moved to
workqueue context causing issue.

Fix:
----
Move Stopping of stale entry timer to Add/Change/Delete
request context instead of workqueue context

Change-Id: I820c25d0462e2459aa7f0d6a84aee5626e8da4f2
Closes-Bug: 1518899
(cherry picked from commit cd6bbe5)
(cherry picked from commit bb2c120)

src/vnsw/agent/ovs_tor_agent/ovsdb_client/ha_stale_l2_route.cc

@@ -46,6 +46,8 @@ bool HaStaleL2RouteEntry::Add() {
         static_cast<HaStaleL2RouteTable *>(table_);
     ack_event_ = KSyncEntry::ADD_ACK;
     table->EnqueueExportEntry(this);
+    // Stop stale clear timer on add/change/delete req
+    StopStaleClearTimer();
     return false;
 }
 
@@ -54,6 +56,8 @@ bool HaStaleL2RouteEntry::Change() {
         static_cast<HaStaleL2RouteTable *>(table_);
     ack_event_ = KSyncEntry::CHANGE_ACK;
     table->EnqueueExportEntry(this);
+    // Stop stale clear timer on add/change/delete req
+    StopStaleClearTimer();
     return false;
 }
 
@@ -62,9 +66,25 @@ bool HaStaleL2RouteEntry::Delete() {
         static_cast<HaStaleL2RouteTable *>(table_);
     ack_event_ = KSyncEntry::DEL_ACK;
     table->EnqueueExportEntry(this);
+    // Stop stale clear timer on add/change/delete req
+    StopStaleClearTimer();
     return false;
 }
 
+void HaStaleL2RouteEntry::StopStaleClearTimer() {
+    // Cancel timer if running
+    if (time_stamp_ != 0) {
+        HaStaleL2RouteTable *table =
+            static_cast<HaStaleL2RouteTable *>(table_);
+        HaStaleDevVnEntry *dev_vn =
+            static_cast<HaStaleDevVnEntry *>(table->dev_vn_ref_.get());
+        HaStaleDevVnTable *dev_vn_table =
+            static_cast<HaStaleDevVnTable*>(dev_vn->table());
+        dev_vn_table->StaleClearDelEntry(time_stamp_, this);
+        time_stamp_ = 0;
+    }
+}
+
 void HaStaleL2RouteEntry::AddEvent() {
     HaStaleL2RouteTable *table =
         static_cast<HaStaleL2RouteTable *>(table_);
@@ -91,14 +111,6 @@ void HaStaleL2RouteEntry::AddEvent() {
                 table->vrf_->GetName() + ", VxlanId " +
                 integerToString(vxlan_id_) + ", MAC " + mac_ + ", dest ip " +
                 table->dev_ip_.to_string());
-
-    // Cancel timer if running
-    if (time_stamp_ != 0) {
-        HaStaleDevVnTable *dev_vn_table =
-            static_cast<HaStaleDevVnTable*>(dev_vn->table());
-        dev_vn_table->StaleClearDelEntry(time_stamp_, this);
-        time_stamp_ = 0;
-    }
 }
 
 void HaStaleL2RouteEntry::ChangeEvent() {
@@ -123,13 +135,6 @@ void HaStaleL2RouteEntry::DeleteEvent() {
                 integerToString(vxlan_id_) + ", MAC " + mac_);
     dev_vn->route_peer()->DeleteOvsRoute(table->vrf_.get(), vxlan_id_,
                                          MacAddress(mac_));
-
-    if (time_stamp_ != 0) {
-        HaStaleDevVnTable *dev_vn_table =
-            static_cast<HaStaleDevVnTable*>(dev_vn->table());
-        dev_vn_table->StaleClearDelEntry(time_stamp_, this);
-        time_stamp_ = 0;
-    }
 }
 
 bool HaStaleL2RouteEntry::Sync(DBEntry *db_entry) {

src/vnsw/agent/ovs_tor_agent/ovsdb_client/ha_stale_l2_route.h

@@ -91,6 +91,8 @@ class HaStaleL2RouteEntry : public OvsdbDBEntry {
 
     void StaleClearCb();
 
+    void StopStaleClearTimer();
+
     void AddEvent();
     void ChangeEvent();
     void DeleteEvent();