As discussed here: https://github.com/fail2ban/fail2ban/issues/1593, the
monitored file has to be present before the fail2ban service starts. Create
this file in a dedicated activation service.
* gnu/tests/security.scm (%auth-log-activation-service): New variable.
(run-fail2ban-basic-test, run-fail2ban-simple-test)
(run-fail2ban-extension-test): Use it.
Fixes: guix/guix#3645
Change-Id: Ic12891cc5438abbd041ceb19e1d22dae51c7c848