Automatic merge from submit-queue

[flake fix] Wait for the podInformer to observe the pod

Fix #29065 

The problem is that the rc manager hasn't observed pod1, so it creates another pod and scales down, pod1 might get deleted. To fix it, wait for the podInformer to observe the pod before running the rc manager.

Marked as P0 as it's fixing a P0 flake.