Added --subnet validation

[shubhbapna]

fixes #15517

Added validateSubnet that makes sure the given subnet has a valid private IP address and if it is cidr then the mask shouldn't be greater than 30

To reduce code duplication, I refactored inspect to use ParseAddr

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[minikube-bot]

Can one of the admins verify this patch?

[shubhbapna]

@spowelljr I have marked it as draft since make lint-ci was failing for me with the following error

cmd/minikube/cmd/start.go:1177:1: cyclomatic complexity 32 of func `validateFlags` is high (> 30) (gocyclo)
func validateFlags(cmd *cobra.Command, drvName string) {
^

But I don't see any way around reducing cyclomatic complexity since I did need to add validateSubnet to this function which adds another path to it. Any suggestions?

[spowelljr]

I think the easiest way to resolve this is to move if driver.BareMetal(drvName) into it's own function and then call it in that func.

func validateBareMetal(cmd *cobra.Command, drvName string) {
        if !driver.BareMetal(drvName) {
                return
        }
        // bare metal validation
}

[spowelljr]

Should wrap this will some helpful text like the others

[spowelljr]

I think you might have forgot to wrap this error

[spowelljr]

I think you might have forgot to wrap this error

[medyagh]

shubhbapna are you still working on this ?

[shubhbapna]

Yep just came back from the holidays! Will start working on it again today

[spowelljr]

Looks good, thank you for the PR

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: shubhbapna, spowelljr

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