Automatic merge from submit-queue

use monotonic now in TestDelNode

Fixes https://github.com/kubernetes/kubernetes/issues/24971.

Briefly, the rate_limited_queue uses a `container/heap` to store values, and use this data structure to ensure we can always fetch the value with the minimum `processAt`. However, in some extreme condition, the continuous call to `time.Now()` would get the same value, which causes some unpredictable order in the queue, this fix uses a monotonic `now()` to avoid that.

@smarterclayton please take a look.