The function for automatically updating the image from master to
slave. When a new device tries to join a stack, the image version is
checked. When this function is enabled, if the image version of the
new device is different from that of the master, the image of the new
device will be updated to be consistent with that of the master.
When this function is disabled, the new device can not join the stack
if the image version of the new device is different from that of the
master.
disabled: disable auto update function
enabled: enable auto update function