[collectd] Add percentage support to df and rrd_update_r complaining about extra argument

[Daniel Hilst]

I'm trying to add percentage support to df plugin, so I can see free 
space in percentage instead of bytes.

I have tried add new value to df_complex on types.db and change 
df_read() and df_submit_one()

It works, but is loging this message for each mount point, for each 
plugin instance (used/free/...)

Feb  6 14:47:36 localhost collectd[26527]: rrdtool plugin: rrd_update_r 
(localhost.localdomain/df-home/df_complex-free.rrd) failed: 
localhost.localdomain/df-home/df_complex-free.rrd: found extra data on 
update argument: 85.675549


Here is the diff generated from my changes:
http://pastebin.com/ZVteG5CH

What I'm missing?

Cheers!