key error when boot_options are not defined.

 Traceback (most recent call last):
  File "/srv/lava<email address hidden>/lava_dispatcher/actions/boot_control.py", line 88, in run
  client.boot_linaro_image()
  File "/srv/lava<email address hidden>/lava_dispatcher/client/base.py", line 442, in boot_linaro_image
  self._boot_linaro_image()
  File "/srv/lava<email address hidden>/lava_dispatcher/client/targetdevice.py", line 76, in _boot_linaro_image
  self.proc = self.target_device.power_on()
  File "/srv/lava<email address hidden>/lava_dispatcher/device/master.py", line 104, in power_on
  self._boot_linaro_image()
  File "/srv/lava<email address hidden>/lava_dispatcher/device/master.py", line 501, in _boot_linaro_image
  elif options['boot_cmds'].value != 'boot_cmds':
 KeyError: 'boot_cmds'