Automatic merge from submit-queue
make client-go more authoritative
Builds on https://github.com/kubernetes/kubernetes/pull/40103
This moves a few more support package to client-go for origination.
1. restclient/watch - nodep
1. util/flowcontrol - used interface
1. util/integer, util/clock - used in controllers and in support of util/flowcontrol
Automatic merge from submit-queue (batch tested with PRs 39475, 38666, 39327, 38396, 39613)
Add checking the nil value
**What this PR does / why we need it**:
Add checking the nil value.
Thanks.
**Special notes for your reviewer**: