Please see the failed build at https://uberchromegw.corp.google.com/i/chromeos/builders/edgar-release/builds/616 and the error messages during HWTest as below:

Autotest instance: cautotest
  11-27-2016 [21:10:54] Created suite job: http://cautotest.corp.google.com/afe/#tab_id=view_job&object_id=87704604
  The suite job has another 2:29:44.795682 till timeout.
  Suite job   [ PASSED ]
  provision   [ FAILED ]
  provision     FAIL: Unhandled DevServerException: CrOS auto-update failed for host chromeos4-row12-rack8-host3: Write failed: Broken pipe