p/cpubyuser: get stats from top instead of ps

The top cpu statistics fit better to the other cpu statistics in munin.

The ps based statistics are calculated as average over the runtime of a
program, which does not neccessarily reflect the current situation.

plugins/system/cpubyuser

@@ -70,9 +70,9 @@ if [ "$1" = "config" ]; then
 	exit
 fi
 
-ps -e -o "%C%U" | \
+top -b -n 1 | tail -n +8 | \
 	awk -v USERS="$USERS" '
-		{ if ($2 != "USER") CPU_USER[$2]+=$1 }
+		{ if ($2 != "USER") CPU_USER[$2]+=$9 }
 		END {
 			others_sum = 0
 			for (user in CPU_USER) {