When we backported
SERVER-50116 to the 4.0 branch, two tests started failing: rollback_cmd_unrollbackable.js and oplog_truncated_on_recovery.js. The 3.6 backport included updates for these tests to keep them passing; let's forward-port the 3.6 updates for these tests to 4.0.
These tests were removed in 4.1.1 (
SERVER-35591) so the backport to 4.2 and 4.4 didn't encounter this problem.