"systemd restart firewalld.service" compounds rules when CleanUpOnExit=no

Issue

• systemd restart firewalld.service compounds rules when CleanUpOnExit=no is set in /etc/firewalld/firewalld.conf.
• firewalld doesn't flush its own nftables table at startup when CleanUpOnExit=no is set in /etc/firewalld/firewalld.conf.
• The nftables maintained by firewalld has grown so significantly after restarts that system is spending excessive time in netfilter code paths with system performance and packet loss occurring as a result.