appliance: Add suggested udevadm monitor command

While debugging some udev issues, I found use of 'udevadm monitor' to
be fairly useful.  Add a suggested debugging command that might be
used, but comment it out.

Thanks: Alasdair Kergon

appliance/init

@@ -115,6 +115,7 @@ fi
 $UDEVD --daemon #--debug
 udevadm trigger
 udevadm settle --timeout=600
+#udevadm monitor -p &
 
 # Disk optimizations.
 # Increase the SCSI timeout so we can read remote images.