Rule statistics are only refreshed once when the node is initialised
Rule statistics are different from rule configuration because the hardware (MockTurtle software actually) can change them at any time.
Currently, both the config and the stats of the rules are updated once when the device starts. This is fine for the wrtd-tool which does "init"->"operation"->"close", but it is not for any application running longer.
As discussed with Tristan, the correct thing to do is to fetch fresh statistics from the MockTurtle anytime one of the
wrtd_attr_get_stat_rule_* functions is called. Additionally, it would be nice if a) we skip the statistics when reading the rule config and b) we maintain the statistics (by reading them first) before rewriting the rules back to the MockTurtle memory.