abort kube-ovn-controller on leader change

[zhangzujian]

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

What type of this PR

• Bug fixes

In some scenarios, leader change is observed while kube-ovn-controller continues running:

PodName:kube-ovn-controller-7d4fd7596f-l9kjg
...
E0811 14:10:16.385233 7 leaderelection.go:367] Failed to update lock: Operation cannot be fulfilled on configmaps "ovn-config": the object has been modified; please apply your changes to the latest version and try again
I0811 14:10:19.070103 7 election.go:76] new leader elected: kube-ovn-controller-7d4fd7596f-kvtpx
E0811 14:46:30.991520       7 leaderelection.go:330] error retrieving resource lock kube-system/ovn-config: Unauthorized
E0811 14:46:34.605041       7 leaderelection.go:330] error retrieving resource lock kube-system/ovn-config: Unauthorized
E0811 14:46:36.637048       7 leaderelection.go:330] error retrieving resource lock kube-system/ovn-config: Unauthorized