Automatic merge from submit-queue

Fix kube-proxy panic when running with "--cleanup-iptables=true"

**What this PR does / why we need it**:
Save the `--cleanup-iptables` config for new ProxyServer when it's true.
Also check if Broadcaster and EventClient are nil to avoid other potential panic.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #48177

**Special notes for your reviewer**:
/cc @ncdc @irake99

**Release note**:

```release-note
NONE
```