Concurrent step downs due to step down via heartbeat and force reconfig should ensure that the term maintained by topology coordinator is set to TopologyCoordinator::_pendingTermUpdateDuringStepDown.

Force reconfig cmd and force reconfig via heartbeat should be able to take care of updating the term & resetting _pendingTermUpdateDuringStepDown (like we do it in unconditional step down) if they cause step down and _pendingTermUpdateDuringStepDown is set.

• Unconditional step down triggered.
• Reconfig gets executed and caused the node to step down.
• ReplicationCoordinatorImpl::_stepDownFinish gets executed now.

This is a 4.0 bug and the fix must be backported.

 Consequence of this bug is that this requires another heartbeat or metadata update (e.g.. during oplog fetching) to update the term again. (see SERVER-28290).