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: I66114f6272b6760620fc55ad429fcec4ec2f3042
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) {