investigate flaky sequential/test-net-GH-5504 on SmartOS

[Trott]

https://ci.nodejs.org/job/node-test-commit-smartos/4589/nodes=smartos16-64/console:

not ok 1235 sequential/test-net-GH-5504
# SERVER 2>NET 17677: listen2 127.0.0.1 12346 4 false undefined
# SERVER 2>NET 17677: _listen2: create a handle
# SERVER 2>NET 17677: bind to 127.0.0.1
# CLIENT 2>NET 17678: createConnection [ { host: '127.0.0.1', port: 12346 }, [Function] ]
# CLIENT 2>NET 17678: pipe false undefined
# /home/iojs/build/workspace/node-test-commit-smartos/nodes/smartos16-64/test/sequential/test-net-GH-5504.js:55
#       throw new Error('hang');
#       ^
# 
# Error: hang
#     at Timeout._onTimeout (/home/iojs/build/workspace/node-test-commit-smartos/nodes/smartos16-64/test/sequential/test-net-GH-5504.js:55:13)
#     at ontimeout (timers.js:365:14)
#     at tryOnTimeout (timers.js:237:5)
#     at Timer.listOnTimeout (timers.js:207:5)
# SERVER 1>listening
  ---
  duration_ms: 2.424

/cc @geek @misterdjules

Maybe /cc @bnoordhuis too as they provided the fix for the last bout of flakiness with this test (although that was on Windows)

[geek]

@Trott I will take a look, this appeared in a test run for me as well: https://ci.nodejs.org/job/node-test-commit-smartos/nodes=smartos16-64/4612/console