Forwards bantime to action scripts

Currently, "bantime" is not forwarded to action scripts which use a default value such as 600 for all jails.
This mean that actions script with integrated timeouts, such as ipset (proto6) will remove the ban after this time, regardless of the bantime that is defined in jail.local or in a particular jail. That mean that in practice, the real duration of the ban is the minimum of the integrated timeout (always 600 unless the action script was modified) and whatever was requested in the jail configuration. This is very unintuitive and results from the fact that there are 2 distinct expiration mechanism that do not share their timeout.

That pulls attemps to correct that, by forwarding the bantime variable to the action script, so that both mechanism use the same timeout.