Add in custom workload type to kube-burner branch

[paigerube14]

Some users might want to have a specific number of namespaces and a set number of pods per namespace. Would be helpful to add in an option to pass your own custom kube-burner config file

Already set up in e2e-benchmark, just need to add the possiblity into jenkins
https://github.com/cloud-bulldozer/e2e-benchmarking/tree/master/workloads/kube-burner#launching-custom-workloads