RHEL8.x compatibility about viya-perf-tool

[jimkuell]

Hey @alan-71. We're working on adding RHEL 8 support, but there's a few hurdles with the network tests that need to be resolved first.

In a nutshell, the tool currently uses iperf2. Iperf3 is the only version available in the default RHEL 8 repos and that version has some fundamental flaws where its single-threaded nature doesn't allow it to push throughput above a threshold of ~40 Gb/s. We're exploring some potential alternatives that will hopefully allow this to run on RHEL 8 in the near future.