Add "fakebios" when booting Linux.

This is needed for Xen to boot.

emulab/grub.cfg

@@ -223,6 +223,10 @@ function linux_boot {
 			set diskroot=$root
 			set root=$oroot
 			handle_grubenv
+
+			# XXX needed to boot Xen
+			fakebios
+
 			echo "Grub config file: '($diskroot)$grubdir/$cfgfile'"
 			configfile ($diskroot)$grubdir/$cfgfile
 		fi