ENI style network configuration with NoCloud datasource does not work on RHEL/Centos

# Bug report

https://cloudinit.readthedocs.io/en/latest/reference/datasources/nocloud.html#example-meta-data

The configuration describe in the document does not work when using RHEL/CentOS :

```
instance-id: iid-abcdefg
network-interfaces: |
iface eth0 inet static
address 192.168.1.10
network 192.168.1.0
netmask 255.255.255.0
broadcast 192.168.1.255
gateway 192.168.1.254
hostname: myhost
```

## Steps to reproduce the problem

Use the meta-data describe https://cloudinit.readthedocs.io/en/latest/reference/datasources/nocloud.html#example-meta-data using the NoCloud datasource with a CentOS or RHEL cloud images. Fedora might also by affected.

## Environment details
- Cloud-init version: 23.x
- Operating System Distribution: RHEL, CentOS
- Cloud provider, platform or installer type: NoCloud

## cloud-init logs