Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

add ProxyModeIPVS in proxy mode validation

**What this PR does / why we need it**:
Currently didn't add "ipvs" in proxy mode check, then if we use "ipvs" mode, will get this error:
'error: KubeProxyConfiguration.Mode.ProxyMode: Invalid value: "ipvs": must be userspace,iptables or blank (blank means the best-available proxy (currently iptables)'
So I added it. 

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

**Special notes for your reviewer**:

**Release note**:
```release-note
NONE
```