Investigate flaky test-dgram-send-callback-buffer on FreeBSD

[Trott]

https://ci.nodejs.org/job/node-test-commit-freebsd/3511/nodes=freebsd10-64/console

not ok 223 parallel/test-dgram-send-callback-buffer
# /usr/home/iojs/build/workspace/node-test-commit-freebsd/nodes/freebsd10-64/test/parallel/test-dgram-send-callback-buffer.js:19
#   throw new Error('Timeout');
#   ^
# 
# Error: Timeout
#     at Timeout._onTimeout (/usr/home/iojs/build/workspace/node-test-commit-freebsd/nodes/freebsd10-64/test/parallel/test-dgram-send-callback-buffer.js:19:9)
#     at tryOnTimeout (timers.js:232:11)
#     at Timer.listOnTimeout (timers.js:202:5)
  ---
  duration_ms: 0.409