I've been trying to verify an alternative fix to  issue 338793  to see if my original workaround could be rolled back, but I've noticed that top of tree v3.18 still is flaky

I'm running the following on a chromeos-3.18 board : 
test_that -b <board> <ip addr> network_DhcpStaticIP network_DhcpWpadNegotiation network_DhcpNonAsciiParameter network_DhcpRenew network_DhcpClasslessStaticRoute

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/tmp/test_that_results_6YM2nt/results-1-network_DhcpStaticIP                                              [  FAILED  ]
/tmp/test_that_results_6YM2nt/results-1-network_DhcpStaticIP                                                FAIL: Test server didn't get all the messages it was told to expect during negotiation.
/tmp/test_that_results_6YM2nt/results-1-network_DhcpStaticIP/network_DhcpStaticIP                         [  FAILED  ]
/tmp/test_that_results_6YM2nt/results-1-network_DhcpStaticIP/network_DhcpStaticIP                           FAIL: Test server didn't get all the messages it was told to expect during negotiation.
/tmp/test_that_results_6YM2nt/results-1-network_DhcpStaticIP/network_DhcpStaticIP                           03/15 14:09:01.772 ERROR|  dhcp_test_server:0225| Test in progress has timed out.
/tmp/test_that_results_6YM2nt/results-2-network_DhcpWpadNegotiation                                       [  PASSED  ]
/tmp/test_that_results_6YM2nt/results-2-network_DhcpWpadNegotiation/network_DhcpWpadNegotiation           [  PASSED  ]
/tmp/test_that_results_6YM2nt/results-3-network_DhcpNonAsciiParameter                                     [  PASSED  ]
/tmp/test_that_results_6YM2nt/results-3-network_DhcpNonAsciiParameter/network_DhcpNonAsciiParameter       [  PASSED  ]
/tmp/test_that_results_6YM2nt/results-4-network_DhcpRenew                                                 [  PASSED  ]
/tmp/test_that_results_6YM2nt/results-4-network_DhcpRenew/network_DhcpRenew                               [  PASSED  ]
/tmp/test_that_results_6YM2nt/results-5-network_DhcpClasslessStaticRoute                                  [  PASSED  ]
/tmp/test_that_results_6YM2nt/results-5-network_DhcpClasslessStaticRoute/network_DhcpClasslessStaticRoute [  PASSED  ]
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Total PASS: 8/10 (80%)

Doesn't fail every time. Need to dig into this. The original bug  issue 338793  was very deterministic, but this seems less so.