Fix applying num_instructions_to_generate to simple pipelines

[russellb]

In #86, I knowingly broke the simple pipelines in favor of restoring desired full pipeline behavior.

8179df5

That commit message explains what is needed to fix the simple ones to use the n parameter as desired. We need a way to specify in config that we want n set to this runtime parameter, since we do not want that for all cases n is not explicitly specified in config.