Improve documentation of multiple interface setup

[laeti-tia]

In our documentation and training, we recommend running perfSONAR tests through different NIC, one for throughput, one for the other tests and yet another one for the management traffic. pScheduler also provides different options to use different interfaces for its management traffic and for the test/tools traffic.

This setup can be a bit complicated and it could help to have a better description of the different traffic flows going in and out of a perfSONAR machine:

• pscheduler management traffic
• tools management traffic (iperf/owamp)
• tools test traffic

[timchown]

The docs also need to describe how to steer traffic over the correct interface, e.g. referring to the host routing and the lead-bind option.

Otherwise you might see pscheduler talking over a different interface to the one trhe test will run on, or archiving traffic trying to use unexpected interfaces.