cni: use hash to generate host-side veth name
cni: use hash to generate host-side veth name

if CNI_CONTAINERID has 1st 5 char same then cni fails
chapman:/home/nirmoy/go/src/github.com/cilium/cilium # CNI_COMMAND=ADD CNI_CONTAINERID=1234567891 CNI_NETNS=/var/run/netns/1234567891 CNI_IFNAME=eth12 CNI_PATH=/opt/cni/bin ./plugins/cilium-cni/cilium-cni < ./plugins/cilium-cni/05-cilium-cni.conf  2>/dev/null >/dev/null
chapman:/home/nirmoy/go/src/github.com/cilium/cilium # CNI_COMMAND=ADD CNI_CONTAINERID=1234567892 CNI_NETNS=/var/run/netns/1234567892 CNI_IFNAME=eth12 CNI_PATH=/opt/cni/bin ./plugins/cilium-cni/cilium-cni < ./plugins/cilium-cni/05-cilium-cni.conf
{
    "code": 100,
    "msg": "unable to create veth pair: file exists"

Signed-off-by: Nirmoy Das <6ad020fa725fa73abb9a553bfe35b16e2f80a6a0@suse.de>

cilium-team/cilium,scanf/cilium,tgraf/cilium,scanf/cilium,michi-covalent/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,tgraf/cilium,scanf/cilium,michi-covalent/cilium,cilium-team/cilium,scanf/cilium,cilium/cilium,tklauser/cilium,michi-covalent/cilium,tgraf/cilium,cilium/cilium,scanf/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,scanf/cilium,cilium/cilium,tgraf/cilium,michi-covalent/cilium,michi-covalent/cilium,scanf/cilium