test: fix flaky test-http-pipeline-flood

PR-URL: #17955
Refs: #16317
Reviewed-By: James M Snell <[email protected]>

Author: apapirovski

test/parallel/test-http-pipeline-flood.js

@@ -56,9 +56,9 @@ function parent() {
       server.close();
     }));
 
-    server.setTimeout(200, common.mustCall(function() {
+    server.setTimeout(200, common.mustCallAtLeast(function() {
       child.kill();
-    }));
+    }, 1));
   });
 }