investigate unreliable test-heapdump-http2 #34389

AssertionError [ERR_ASSERTION]: Expect to find 1 'Node / StreamPipe', found 0
    at State.validateSnapshot (/Users/trott/io.js/test/common/heap.js:122:14)
    at State.validateSnapshotNodes (/Users/trott/io.js/test/common/heap.js:186:10)
    at ClientHttp2Stream.<anonymous> (/Users/trott/io.js/test/pummel/test-heapdump-http2.js:60:11)
    at ClientHttp2Stream.<anonymous> (/Users/trott/io.js/test/common/index.js:365:15)
    at ClientHttp2Stream.emit (events.js:314:20)
    at emit (internal/http2/core.js:299:8)
    at processTicksAndRejections (internal/process/task_queues.js:83:22) {
  generatedMessage: false,
  code: 'ERR_ASSERTION',
  actual: 0,
  expected: 1,
  operator: 'strictEqual'
}