uptime should report days, not seconds

Source: https://sourceforge.net/p/muninlite/patches/8/
Author: Craig Gallek

See patch "110-fix-uptime-days" in OpenWrt.

plugins/uptime

@@ -4,8 +4,7 @@ config_uptime() {
   echo "graph_vlabel uptime in days"
   echo "uptime.label uptime"
   echo "uptime.draw AREA"
-  echo "uptime.cdef uptime,86400,/"
 }
 fetch_uptime() {
-  echo "uptime.value" $(cut -d\  -f1 /proc/uptime)
+  awk '{printf "uptime.value %.2f",$1/86400; print ""}' /proc/uptime
 }