Ghost BGP session could not be cleaned

I still got “Duplicate BGP session” error even if hold timer expired.

2014-09-28 20:43:25.255 PDT [nettyThreadgroupModule$NioEventLoopGroupCloseable-7-2] INFO o.o.p.bgp.rib.impl.BGPSessionImpl - Failed to send message Keepalive [augmentation=[]] to socket java.nio.channels.ClosedChannelException
2014-09-28 20:43:45.257 PDT [nettyThreadgroupModule$NioEventLoopGroupCloseable-7-2] INFO o.o.p.bgp.rib.impl.BGPSessionImpl - Failed to send message Keepalive [augmentation=[]] to socket java.nio.channels.ClosedChannelException
2014-09-28 20:43:59.256 PDT [nettyThreadgroupModule$NioEventLoopGroupCloseable-7-2] INFO o.o.p.bgp.rib.impl.BGPSessionImpl - Failed to send message Notify [_errorCode=4, _errorSubcode=0, augmentation=[]] to socket java.nio.channels.ClosedChannelException
2014-09-28 20:43:59.258 PDT [nettyThreadgroupModule$NioEventLoopGroupCloseable-7-2] INFO o.o.protocol.bgp.rib.impl.BGPPeer - Session with peer 147.128.12.112 terminated: BGPTerminationReason

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osgi> 2014-09-28 22:20:39.804 PDT [nettyThreadgroupModule$NioEventLoopGroupCloseable-7-1] WARN o.o.p.b.r.impl.StrictBGPPeerRegistry - Duplicate BGP session established with IpAddress [_ipv4Address=Ipv4Address [_value=147.128.12.112], _value=[1, 4, 7, ., 1, 2, 8, ., 1, 2, ., 1, 1, 2]]

Test step:
1. Start BGP peer.
2. Shut down BGP peer.
3. Wait for hold timer expired.
4. Re-start BGP peer.