RPS mode breaks warmup

[leokondrashov]

Version

main branch

Steps to reproduce

1. Create cluster with ./scripts/setup/create_multinode.sh
2. Run loader.go with cmd/config_knative_rps.json with non-zero number in WarmupDuration

Expected behavior

Run for WarmupDuration + ExperimentDuration number of minutes; mark first WarmupDuration minutes with phase 1, rest with phase 2

Observed behavior

Fail with following message:

WARN[Jan 27 00:02:27.201] It is recommended that the first 10% of cold starts are discarded from the experiment results for low cold start RPS.
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0x99e667]

goroutine 1 [running]:
github.com/vhive-serverless/loader/pkg/trace.profileConcurrency(...)                                                                                                                                                     /users/lkondras/loader/pkg/trace/trace_profiler.go:87
github.com/vhive-serverless/loader/pkg/trace.DoStaticTraceProfiling({0xc0001ce8e0, 0x3, 0xc00025fbc8?})                                                                                                                  /users/lkondras/loader/pkg/trace/trace_profiler.go:38 +0x107
github.com/vhive-serverless/loader/pkg/driver.(*Driver).RunExperiment(0xc0001d1a40)                                                                                                                                      /users/lkondras/loader/pkg/driver/trace_driver.go:512 +0x38
main.runRPSMode(0xc0001cdd40, 0x0, 0x0)                                                                                                                                                                                  /users/lkondras/loader/cmd/loader.go:250 +0x2a7
main.main()                                                                                                                                                                                                              /users/lkondras/loader/cmd/loader.go:110 +0x405
exit status 2