feedback_daemon: speedup the first send to 2 minutes

The first send should happen sooner, than default feedback interval, to
catch not so long-living instances. This replaces the commit we had with
sending feedback right from initial box.cfg{} and on first event
appearance, such as creation/drop of a space or index.

The reason for this commit instead of "send feedback on server start",
is that the latter one was quite hacky and didn't work correctly without
some ugly crutches, namely, fiber.sleep(10) in feedback daemon code.

Follow-up #5750

(cherry picked from commit 843fa23e74178b5eb1519e78cff36bad88b03587)