Fix ipset fails when fail2ban restarts

[tomers]

Fixes fail2ban fails when restarting, due to the ipset being persistent, and the actionstart command tries to recreate existing set, and fails since this set already exists.

[sebres]

Fixes fail2ban fails when restarting, due to the ipset being persistent

How so?
Where is it persistent?
It looks either like a misunderstanding or misconfiguration to me.
Because corresponding this:

fail2ban/config/action.d/iptables-ipset-proto4.conf

Line 46 in 8eac5f5

ipset --destroy f2b-<name>

the set gets removed (actionstop will be invoked by restart too).

As for misconfiguration, for instance it may be mistakenly supplied common <name> for two different jails.
Or some error by stop that avoid the set removal.

[Neustradamus]

@tomers: Have you seen @sebres comment?

[tomers]

I am pretty sure it happend to me. I have no time at the moment to recheck. However, just create a chain, and then restart the fail2ban service. If it works, then you can close this ticket.
Sorry for not being able to be more helpful.