Enqueue route updates in fabric route tables.

There are still a couple of places where enqueue is happening in
respective VRF route tables. As these may be deleted before the
enqueued request is handled, always enqueue in fabric route table,
which checks for the actual route table and invokes relevant
operation.

Change-Id: I030291f68c1e000bcd9c8acc98285805ce08c791
closes-bug: 1544380

src/vnsw/agent/oper/inet_unicast_route.cc

@@ -116,8 +116,7 @@ static void Inet4UnicastTableEnqueue(Agent *agent, DBRequest *req) {
 
 static void Inet6UnicastTableEnqueue(Agent *agent, const string &vrf_name,
                                      DBRequest *req) {
-    AgentRouteTable *table =
-        agent->vrf_table()->GetInet6UnicastRouteTable(vrf_name);
+    AgentRouteTable *table = agent->fabric_inet4_unicast_table();
     if (table) {
         table->Enqueue(req);
     }

src/vnsw/agent/oper/path_preference.cc

@@ -392,9 +392,9 @@ void PathPreferenceSM::EnqueuePathChange() {
 
     AgentRouteTable *table = NULL;
     if (rt_->GetTableType() == Agent::EVPN) {
-        table = rt_->vrf()->GetEvpnRouteTable();
+        table = agent_->fabric_evpn_table();
     } else if (rt_->GetTableType() == Agent::INET4_UNICAST) {
-        table = rt_->vrf()->GetInet4UnicastRouteTable();
+        table = agent_->fabric_inet4_unicast_table();
     }
 
     if (table) {