Fix DNS override not surviving reboot

[csibbitt]

• use nmcli to set it in NetworkManager instead of blindly writing to resolv.conf

[csibbitt]

Old code

Before running the ansible

$ ssh gpu-validation -- cat /etc/resolv.conf
# Generated by NetworkManager
search openstackgate.local
nameserver 172.30.0.10

After running the ansible

$ ansible-playbook -i inventory-local --skip-tags rhoso -e gpu_validation_dns_server=192.168.25.10 main.yaml
[...]
TASK [gpu-validation : Overwrite DNS entries in /etc/resolv.conf if gpu_validation_dns_server is set] ******************************************************************************
changed: [gpu-validation-0]
[...]

$ ssh gpu-validation -- cat /etc/resolv.conf
nameserver 192.168.25.10

After reboot

$ ssh gpu-validation -- sudo reboot
Connection to 192.168.25.222 closed by remote host.

$ ssh gpu-validation -- cat /etc/resolv.conf
# Generated by NetworkManager
search openstackgate.local
nameserver 172.30.0.10

This is the problem to solve - after reboot (or other NM event, perhaps), the nameserver is set back to 172.30.0.10 instead of the 192.168.25.10 we configured.

New code

After running the ansible

$ ansible-playbook -i inventory-local --skip-tags rhoso -e gpu_validation_dns_server=192.168.25.10 main.yaml
[...]
TASK [gpu-validation : Set DNS server using nmcli if gpu_validation_dns_server is set] *********************************************************************************************
changed: [gpu-validation-0]

[...]

$ ssh gpu-validation --  cat /etc/resolv.conf 
# Generated by NetworkManager
nameserver 192.168.25.10

After reboot

$ ssh gpu-validation -- sudo reboot
Connection to 192.168.25.222 closed by remote host.

$ ssh gpu-validation -- cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 192.168.25.10

[MiguelCarpio]

LGTM