do not exit if chassis is not found

[zhangzujian]

Pull Request

• 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

I0701 15:24:37.427598      13 node.go:899] chassis not registered for node kube-ovn-control-plane, do chassis gc once
I0701 15:24:37.427716      13 gc.go:738] start to gc chassis
E0701 15:24:37.428693      13 init.go:859] chassis not registered for node kube-ovn-control-plane, will try again later
E0701 15:24:37.428893      13 klog.go:10] "failed to initialize node chassis" err="chassis not registered for node kube-ovn-control-plane, will try again later"