Use same collectd df options as StackLight MOS

linux/files/collectd_df.conf

@@ -7,4 +7,8 @@
   FSType {{ fs_type }}
   {%- endfor %}
   IgnoreSelected {{ plugin.get('ignore_selected', False)|lower }}
+  ReportByDevice false
+  ReportInodes true
+  ValuesAbsolute true
+  ValuesPercentage true
 </Plugin>