simultaneous graceful leaving of two nodes leaves one remaining in non-PC

Sometimes when two out of three nodes leave the cluster almost simultaneously, the remaining node may end up in non-PC even if the nodes left gracefully.

Here is what happens:

1) Node 1 leaves the cluster, nodes 2 and 3 get the notification from EVS layer that node 1 left
2) Nodes 2 and 3 exchange states to form new PC view, but node 2 decides to leave just before message exchange is complete
3) Because forming new PC view was interrupted, node 3 loses the information that node 1 left gracefully, so final quorum computation for singleton view results non-PC

Expected behavior would be that the status of node 1 leaving gracefully would be preserved over intermediate view changes.

Note that if nodes 1 and 2 leave cluster so simultaneously that node 3 gets the notification of it in single view change or if nodes 2 and 3 finish the message exchange for new PC view before node 2 leaves, the outcome is that node 3 ends up in PC as expected.