fix: adjust cli flags for perf runner for testing purposes

[maschad]

Follow up PR related to #258

Based on @mxinden 's comments regarding the perf runner

[mxinden]

This is great. Thank you!

[achingbrain]

Not sure why, maybe I'm not doing it right, but when I set testing to true, suddenly the runner can't find the iperf3 binary:

= run 1 iPerf TCP from client to server
Warning: Permanently added '54.191.84.202' (ED25519) to the list of known hosts.
cat: pidfile: No such file or directory
kill: usage: kill [-s sigspec | -n signum | -sigspec] pid | jobspec ... or kill -l [sigspec]
rm: cannot remove 'pidfile': No such file or directory
rm: cannot remove 'server.log': No such file or directory


bash: line 1: iperf3: command not found
Error: Command failed: ssh -o StrictHostKeyChecking=no ec2-user@3.95.55.203 'iperf3 -c 54.191.84.202 -t 1 -N'
bash: line 1: iperf3: command not found

https://github.com/libp2p/test-plans/actions/runs/6904729515/job/18785974329