The two_nodes_priority_takeover.js test does a reconfig to swap the priority of two nodes in a replica set, and then expects the new, higher priority node to take over and become primary. Right now, it uses this reconfig helper which may execute a single config change as a series of multiple reconfigs. This makes the test unstable, since the final reconfig executed by that helper may occur after the priorities have switched, so it may interfere with the nodes stepping down. We should execute the reconfig with a plain reconfig command so it can happen in a single step and avoid this issue.