setdiscovery: avoid calling any sample building if the undecided set is small If the length of undecided is smaller than the sample size, we can just request information for all of them. This conditional was previously handled by '_setupsample'. But '_setupsample' is in my opinion a problematic function with blurry semantics. Having this conditional explicitly earlier makes the code more explicit and moves us closer to removing this '_setupsample' function.