Fix excessive logging in idle slotsync worker.

Fix excessive logging in idle slotsync worker.

The slotsync worker was incorrectly identifying no-op states as successful
updates, triggering a busy loop to sync slots that logged messages every
200ms. This patch corrects the logic to properly classify these states,
enabling the worker to respect normal sleep intervals when no work is
performed.

Reported-by: Fujii Masao <masao.fujii@gmail.com>
Author: Zhijie Hou <houzj.fnst@fujitsu.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: shveta malik <shveta.malik@gmail.com>
Backpatch-through: 17, where it was introduced
Discussion: https://postgr.es/m/CAHGQGwF6zG9Z8ws1yb3hY1VqV-WT7hR0qyXCn2HdbjvZQKufDw@mail.gmail.com