Comment 7 for bug 1736674

So it looks that there is kind of race condition here.
First instance of IptablesManager object is created in iptables_firewall driver and it applies wanted SG rules in filters table.
But than another instance of IptablesManager is created in LB qos driver and when "delete_dscp_marking" method is called it tries to remove QoS related rules from iptables. That works fine but as this second instance of IptablesManager don't have any rules in "filters" or "raw" tables it cleans it in _apply_synchronize method.