Don't exit on unknown device types (#260)

I get `disk type is not sat, scsi, nvme or megaraid but sntrealtek`,
which aborts the whole run for no reason.

Looks like a 13 year old bug :)

Signed-off-by: Matt Joiner <anacrolix@gmail.com>

Author: anacrolix

smartmon.sh

@@ -200,7 +200,7 @@ for device in ${device_list}; do
   usbprolific) smartctl -A -d "${type}" "${disk}" | parse_smartctl_attributes "${disk}" "${type}" ;;
   *)
       (>&2 echo "disk type is not sat, scsi, nvme or megaraid but ${type}")
-    exit
+    continue
     ;;
   esac
 done | format_output