__ipset: explorer/content, a better way to find the start of the set membership

Don't count lines, as that seems inconsistant, instead find the start of the membership list by looking for "Members:"

cdist/conf/type/__ipset/explorer/content

@@ -20,7 +20,7 @@
 
 name="$__object_id"
 if ipset -t list | grep -qP "Name: $name"; then
-    ipset list "$name" | tail -n +9
+    ipset list "$name" | sed '0,/^Members:/d'
 else
     echo "x_missing_x"
 fi