[PATCH v2 3/4] examples/ipsec-secgw: fix buffer free logic in vector mode

[Akhil Goyal]

> Fix packet processing to skip after mbuf is freed instead of
> touching and Tx'ing it.
> 
> Also free vector event buffer in event worker when after processing
> there is no pkt to be enqueued to Tx adapter.
> 
> Fixes: 86738ebe1e3d ("examples/ipsec-secgw: support event vector")
> Cc: schalla at marvell.com
> Cc: stable at dpdk.org
> 
> Signed-off-by: Nithin Dabilpuram <ndabilpuram at marvell.com>
Acked-by: Akhil Goyal <gakhil at marvell.com>