Eliminate spurious periodic.daily error message for rotating accounting log.

In 2011, r218961 removed local code for rotating logs in favor of using the
rotate_log command in etc/rc.d/accounting. If the accounting service is
activated then subsequently de-activated in rc.conf but still remains active
in periodic.conf, then you get an error message every day in the periodic
jobs about being unable to rotate the logs.

With this change to use "onerotate_log", the log rotation will happen the
first time periodic daily runs after accounting was disabled but periodic
accounting was left enabled. After that happens once, the /var/account/acct
will no longer exist, which results in a different path through the periodic
code and no more error messages will appear (unless daily_show_badconfig is
set, in which case the admin will be told that periodic security processing
is enabled but the accounting file is not present).

This is only a partial fix for the problems reported in PR 202203.

PR: 202203