cni-server: wait ovs-vswitchd to be running

[zhangzujian]

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

What type of this PR

• Bug fixes

Which issue(s) this PR fixes:

In #2516 we removed the IP/route transfer logic in start-ovs.sh and all underlay bridges will be deleted after the node reboot before ovs-vswitchd starts up. However, there is a chance that kube-ovn-cni starts before the bridge deletion completes, and uses a non-existent ovs bridge as the tunnel interface.

This patch fixes the bug by making kube-ovn-cni wait for ovs-vswitchd to run.

WHAT

copilot:summary

copilot:poem

HOW

copilot:walkthrough

[github-actions]

• The script can be improved by adding a timeout to the while loop. If OVS_SOCK is not found within a certain amount of time, the script should exit with an error message.
• Instead of using sleep(1) to wait for OVS_SOCK, it would be better to use inotifywait or a similar tool to monitor the file system for changes to the socket file.
• The script should check if OVS_SOCK exists before entering the while loop. If it does not exist, the script should exit with an error message.
• The echo statement inside the while loop should be removed or moved outside the loop to avoid unnecessary output.
• It would be better to use a more descriptive variable name than OVS_SOCK, such as OVS_SOCKET_FILE.