VNet/Vxlan delete handling (sonic-net#766)

* Route/NH and VNet delete handling

* Handle VNET Route with Nexthop IP, fix route remove

* Address review comments, increment CRM counters,

Author: prsunny

orchagent/intfsorch.cpp

@@ -155,6 +155,7 @@ bool IntfsOrch::setIntf(const string& alias, sai_object_id_t vrf_id, const IpPre
         return false;
     }
 
+    vrf_id = port.m_vr_id;
     addSubnetRoute(port, *ip_prefix);
     addIp2MeRoute(vrf_id, *ip_prefix);