reconfig can occasionally lead to the primary stepping down. This means that the guarantee we thought
SERVER-20844 gave us, of being a stable replicaset with node 0 as primary, is not always guaranteed. To address this, we should call awaitNodesAgreeOnPrimary() and then make sure that node 0 is the primary. If it is not, we should step up node 0 to primary. In PV1 we can use replSetStepUp on node 0 to accomplish this. In PV0, we can repeatedly call replSetStepDown on the primary with a high step down timeout until node 0 is elected. At that point we can call replSetFreeze on every node with a freeze timeout of 0 to allow them all to run for election immediately if they want to.