support for ipv6 addresses

[jostreff]

It crashes when into xml files, we use ipv6 addresses.

json file was generated using command "iperf3 -s --bind-dev enp4s0f0 --json --forceflush --logfile /tmp/iperf3.xml"

iperf3.xml

[jostreff]

actually it looks that problem is not in ipv6 address but it is that in one file there are multiple measurements written.

[jostreff]

I have modified your script, so it now supports multi line json file, generated with multiple attempts.

iperf_plotter_array.py