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validate ipvs scheduler
**What this PR does / why we need it**:
validate ipvs scheduler options
**Which issue this PR fixes**:
closes#53975
**Special notes for your reviewer**:
It depends on work of #53780.
**Release note**:
```release-note
NONE
```
/sig network
/area kube-proxy
In iptables/proxier.go, there is code to check the length of the
CIDR and setup nat/iptables only if the length of the string is
greater than zero. However in PR #49087, strong validation was
added so kube proxy currently bails out and basically mandates
a valid cidr has to be specified. Let us go back to the earlier
behavior.
