Feature/fix dns setup for Proxmox

[vladyslavpro01]

this fixes DNS setup for Proxmox
related to #56

I've tested the _set_interface_dns it was not working, that's why I've changed it to a native os command call

[ader1990]

Hello,

We are currently using opendev for patches:
https://review.opendev.org/q/project:x/cloudbase-init

How to create an account and contribute to:
https://docs.openstack.org/contributors/common/setup-gerrit.html

Thank you,
Adrian Vladu.

[Puben]

Hi - This relevant feature/fix does not seem to be added to OpenDev.
Id like to contribute but perhaps not my place to take the edits proposed by @vladyslavpro01 and add it to OpenDev.

[ader1990]

Hello @Puben @vladyslavpro01, the first commit that changes the dns regex can be merged if a small patch is added to opendev. The second commit seems to be breaking the backwards compatibility -- why is the second commit needed?

Thank you.