scale_openshift_wrapper should expose parameters to target machineset from different labels

[afcollins]

Currently, trigger_scale.py hard-codes the machineset labels used for the scale task.

As a tester, I need to be able to target certain machinesets for certain workload tests, and would like to configure a single variable that influences this behavior.

Would require similar changes through benchmark-operator and perhaps higher up the stack.

Hard-coded labels: https://github.com/cloud-bulldozer/benchmark-wrapper/blob/master/snafu/scale_openshift_wrapper/trigger_scale.py#L181-L184 https://github.com/cloud-bulldozer/benchmark-wrapper/blob/master/snafu/scale_openshift_wrapper/trigger_scale.py#L219-L222 https://github.com/cloud-bulldozer/benchmark-wrapper/blob/master/snafu/scale_openshift_wrapper/trigger_scale.py#L305 https://github.com/cloud-bulldozer/benchmark-wrapper/blob/master/snafu/scale_openshift_wrapper/trigger_scale.py#L319