The safe reconfig protocol ensures only one reconfig can happen at a time (on a given node), and reconfig cancels elections. However, a node that has learned about a new config via heartbeat and is beginning to process it could suddenly start to step down. Let's investigate whether there are concurrency issues in these scenarios.

1. node has started to step down and suddenly learns about a new config via heartbeat
2. a node has learned about a new config via heartbeat, but suddenly starts to step down
3. a node has started to step down and suddenly a replSetReconfig command arrives from the user
4. a replSetReconfig command arrives from the user and suddenly the node starts to step down