Correct the problem of reumount operation

Text mode uses python-newt to show install progress

	modified:   interface/ri_inst_cli.py
	modified:   interface/ri_install.py
	modified:   operation/exec_finish_install.sh
	modified:   operation/functions
	modified:   operation/partition_disks.sh

operation/functions

@@ -99,7 +99,7 @@ reumount ()
 	else
 		# delete last "/" in mountpoint
 		# mountpoint in /proc/mounts don't have "/" at last
-		multi_mountpoint=$(echo arg|sed "s%/$%%")
+		multi_mountpoint=$(echo $arg|sed "s%/$%%")
 	fi
 
 	# may be a device has been mounted in multi-mountpoint.