message: fix(api): apiv2: correctly set smoothie speed
  was actually broken in its
  implementation, because if update=false the old saved speed would be set instead
  of the new value. This fixes the issue.
diff: @@ -655,7 +655,7 @@ class SmoothieDriver_3_0_0:
  ''' set total axes movement speed in mm/second'''
  if update:
  self._combined_speed = float(value)
  - speed_per_min = int(self._combined_speed * SEC_PER_MIN)
  + speed_per_min = int(float(value) * SEC_PER_MIN)
  command = GCODES['SET_SPEED'] + str(speed_per_min)
  log.debug("set_speed: {}".format(command))
  self._send_command(command)
  