VM delete doesnot removed all related flows(i.e specific to VMs)

Build#: Lithium-SR1 Build
Openstack: stable/kilo
Neutron Plugin:
enable_plugin networking-odl https://github.com/stackforge/networking-odl stable/kilo

Problem:
=========
When creating the VM's(VM1: Mac: fa:16:3e:b7:a1:ff IP:3.1.1.4),the following flow entries has been created specific to VM

cookie=0x0, duration=616.567s, table=0, n_packets=147, n_bytes=13626, in_port=3,dl_src=fa:16:3e:b7:a1:ff actions=set_field:0x43b->tun_id,load:0x1->NXM_NX_REG0[],goto_table:20
cookie=0x0, duration=616.635s, table=40, n_packets=120, n_bytes=11682, priority=36001,ip,in_port=3,dl_src=fa:16:3e:b7:a1:ff,nw_src=3.1.1.4 actions=goto_table:50

When deleted the VM's following flow doesn't removed from ovs-vsswitch

cookie=0x0, duration=616.635s, table=40, n_packets=120, n_bytes=11682, priority=36001,ip,in_port=3,dl_src=fa:16:3e:b7:a1:ff,nw_src=3.1.1.4 actions=goto_table:50

This stale flow entries retained until unstack the compute node (where VM spawned).

On ODL Side,
When deleting the VM,it thrown with NullPointerException.