sd-event: always reshuffle time prioq on changing online/offline state

Before 81107b84, the compare functions
for the latest or earliest prioq did not handle ratelimited flag.
So, it was ok to not reshuffle the time prioq when changing the flag.

But now, those two compare functions also compare the source is
ratelimited or not. So, it is necessary to reshuffle the time prioq
after changing the ratelimited flag.

Hopefully fixes #19903.

(cherry picked from commit 2115b9b6)

Hopefully fixes #20285 and
https://bugzilla.redhat.com/show_bug.cgi?id=1984651.