We reboot the DUT a few times during provision, and we often fail to SSH into the DUT after such a reboot. Exactly when this SSH failure happens is critical -- if it happened before any update, it is likely to be an infra issue. If it happened after rootfs update, it is more likely to be a problem with the image.

Currently, all these failures look identical in status.log:
  Traceback (most recent call last):
    File "/usr/local/autotest/client/common_lib/test.py", line 806, in _call_test_function
      return func(*args, **dargs)
    File "/usr/local/autotest/client/common_lib/test.py", line 470, in execute
      dargs)
    File "/usr/local/autotest/client/common_lib/test.py", line 347, in _call_run_once_with_retry
      postprocess_profiled_run, args, dargs)
    File "/usr/local/autotest/client/common_lib/test.py", line 380, in _call_run_once
      self.run_once(*args, **dargs)
    File "/usr/local/autotest/server/site_tests/provision_AutoUpdate/provision_AutoUpdate.py", line 121, in run_once
      with_cheets=with_cheets)
    File "/usr/local/autotest/server/afe_utils.py", line 124, in machine_install_and_update_labels
      *args, **dargs)
    File "/usr/local/autotest/server/hosts/cros_host.py", line 815, in machine_install_by_devserver
      force_original=force_original)
    File "/usr/local/autotest/client/common_lib/cros/dev_server.py", line 2355, in auto_update
      error_msg % (host_name, real_error))
  DevServerException: CrOS auto-update failed for host chromeos2-row7-rack6-host19: 0) SSHConnectionError: ssh: connect to host chromeos2-row7-rack6-host19 port 22: Connection timed out
  , 1) SSHConnectionError: ssh: connect to host 100.115.230.65 port 22: Connection timed out


Insert a failure message saying exactly when the SSH failed so that it is easier to classify these failure types.