flow: fix ipv6 address for UDP client
flow: fix ipv6 address for UDP client

skydive-project/skydive,safchain/skydive,skydive-project/skydive,safchain/skydive,lebauce/skydive,safchain/skydive,safchain/skydive,lebauce/skydive,skydive-project/skydive,skydive-project/skydive,skydive-project/skydive,lebauce/skydive,safchain/skydive,lebauce/skydive,lebauce/skydive,skydive-project/skydive,safchain/skydive,lebauce/skydive,safchain/skydive,safchain/skydive,lebauce/skydive,skydive-project/skydive,lebauce/skydive