stop install if user declines

On the final prompt during configuration, if the user hits [enter] -- not realizing that the default answer [n] will cancel the install -- they will get this message:

    The system will now finish configuration and reboot. Please wait...

... followed by some nasty errors, like this:

    mv: cannot rename /tmp_config to /usbkey/config: No such file or directory /smartdc/bin/smartos_pompt_config.sh: line 673: /usb/key/shadow: No such file or directory

... then the server reboots and the configuration starts over again -- which makes it look like the install tried, but failed. 

It happened to me, and I can't be the only idiot...right?