Remove old featureGate flag in Readme

[johscheuer]

What this PR does / why we need it:

This PR corrects the Readme for ipvs mode: https://github.com/kubernetes/kubernetes/blob/master/pkg/proxy/ipvs/README.md. kubeadm init doesn't support the --feature-gates=SupportIPVSProxyMode=true flag anymore since IPVS is in beta and not alpha anymore.

sudo kubeadm init --help
Run this command in order to set up the Kubernetes master.

Usage:
  kubeadm init [flags]

Flags:
      --apiserver-advertise-address string      The IP address the API Server will advertise it's listening on. Specify '0.0.0.0' to use the address of the default network interface.
      --apiserver-bind-port int32               Port for the API Server to bind to. (default 6443)
      --apiserver-cert-extra-sans stringSlice   Optional extra Subject Alternative Names (SANs) to use for the API Server serving certificate. Can be both IP addresses and DNS names.
      --cert-dir string                         The path where to save and store the certificates. (default "/etc/kubernetes/pki")
      --config string                           Path to kubeadm config file. WARNING: Usage of a configuration file is experimental.
      --cri-socket string                       Specify the CRI socket to connect to. (default "/var/run/dockershim.sock")
      --dry-run                                 Don't apply any changes; just output what would be done.
      --feature-gates string                    A set of key=value pairs that describe feature gates for various features. Options are:
CoreDNS=true|false (ALPHA - default=false)
DynamicKubeletConfig=true|false (ALPHA - default=false)
SelfHosting=true|false (ALPHA - default=false)
StoreCertsInSecrets=true|false (ALPHA - default=false)
      --ignore-preflight-errors stringSlice     A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.
      --kubernetes-version string               Choose a specific Kubernetes version for the control plane. (default "stable-1.9")
      --node-name string                        Specify the node name.
      --pod-network-cidr string                 Specify range of IP addresses for the pod network. If set, the control plane will automatically allocate CIDRs for every node.
      --service-cidr string                     Use alternative range of IP address for service VIPs. (default "10.96.0.0/12")
      --service-dns-domain string               Use alternative domain for services, e.g. "myorg.internal". (default "cluster.local")
      --skip-token-print                        Skip printing of the default bootstrap token generated by 'kubeadm init'.
      --token string                            The token to use for establishing bidirectional trust between nodes and masters.
      --token-ttl duration                      The duration before the bootstrap token is automatically deleted. If set to '0', the token will never expire. (default 24h0m0s)

Special notes for your reviewer:
Used kubeadm version:

sudo kubeadm version
kubeadm version: &version.Info{Major:"1", Minor:"9", GitVersion:"v1.9.3", GitCommit:"d2835416544f298c919e2ead3be3d0864b52323b", GitTreeState:"clean", BuildDate:"2018-02-07T11:55:20Z", GoVersion:"go1.9.2", Compiler:"gc", Platform:"linux/amd64"}

Release note:

NONE

[xiangpengzhao]

👍

[Lion-Wei]

Thanks

[xiangpengzhao]

/ok-to-test
/cc @Lion-Wei

[Lion-Wei]

friendly ping @m1093782566

[m1093782566]

/assign

We should also enable IPVS in feature gates by default so that making it work, xref: #60540

[Lion-Wei]

Is this means we don't have to add featureGates in kubeproxy config?

[m1093782566]

/lgtm

[m1093782566]

/approve no-issue

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: johscheuer, m1093782566

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[m1093782566]

Is this means we don't have to add featureGates in kubeproxy config?

Not really... We should keep the feature gates until IPVS goes to GA,

[k8s-github-robot]

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions here.