[PATCH v4] net/kni: reset rte_kni_conf struct before initialization

[Harold Huang]

The problem this patch wants to solve can be reproduced by ovs-dpdk:

1. create a kni  port in ovs:
ovs-vsctl add-port ovs-br0 kni0 -- set Interface kni0 type=dpdk
options:dpdk-devargs=net_kni0

2. change the mtu of the kni device in kernel:
ip link set kni0  mtu 1500

If we do not set rte_kni_conf to 0, the min_mtu and max_mtu are random
and change mtu could be failed.