controller: fix apiserver connection timeout on startup

[zhangzujian]

• Make sure you have followed Kube-OVN Code Style.

What type of this PR

Examples of user facing changes:

• Features
• Bug fixes
• Docs
• Tests

Which issue(s) this PR fixes:

After node reboot, there is a chance that kube-ovn-controller/kube-ovn-cni reports connection timeout and crashes.

This patch makes the controller try to connect the apiserver service's TCP port before creating the k8s client(s).

I0324 09:55:26.024115       7 config.go:247] no --kubeconfig, use in-cluster kubernetes config
W0324 09:55:26.036828       7 k8s.go:28] failed to dial 10.96.0.1:443: dial tcp 10.96.0.1:443: connect: connection refused
W0324 09:55:32.031709       7 k8s.go:28] failed to dial 10.96.0.1:443: dial tcp 10.96.0.1:443: i/o timeout
I0324 09:55:32.044155       7 config.go:305] no --kubeconfig, use in-cluster kubernetes config