After running the cloud-init service, the machine is not pingable.

# Bug report

After running the cloud-init service, the machine is not pingable.

## Steps to reproduce the problem

1、Configure the machine with a static IP
2、systemctl disable NetworkManager.service
3、systemctl enable network
4、reboot

## Environment details
- Cloud-init version:21.4
- Operating System Distribution: openEuler

## cloud-init logs

The key logs are as follows:
```
__init__.py[DEBUG]: Searching for local data source in: ['DataSourceOpenStackLocal']
... ...
util.py[DEBUG]: Read 449 bytes from /var/tmp/cloud-init/cloud-init-dhcp-5p5sey73/dhcp.leases
dhcp.py[DEBUG]: Received dhcp lease on eth_main for x.x.x.x/255.255.254.0 (x.x.x.x is the static ip)
... ...
subp.py[DEBUG]: Running command ['ip', '-family', 'inet', 'link', 'set', 'dev', 'eth_main', 'down'] with allowed return codes [0] (shell=False, capture=True)
... ...
```

Start by reproducing the issue with a static IP on openEuler using the listed systemctl steps. Inspect the cloud-init log entries around __init__.py, dhcp.py, and subp.py, especially the DHCP lease and interface-down command. Done means the machine remains pingable after the cloud-init service runs.

Written by the indexing model from the issue text.