On package installation the uci_default is run before service start.
As the last step in uci_default the Firewall is reloaded but rule inject
fails due to missing ipset.
In normal operation the sentinel-dynfw-client is started before firewall
but during installation this can't be done.

The solution is to just create ipset anytime we start firewall. This
makes it so rules is always added and it really doesn't matter who
creates the ipset. With this either sentinel-dynfw-client creates it or
firewall, which ever comes first.