In the current 1.5 code base, the container network sets dns_enable to true by default. This binds UDP port 53 to the network interface created for the container network. If a container wanted to run a DNS server using that port you would need to have dns_enable set to false when the container network is created.

I propose added a new configuration for the container network "disable-dns" to set the dns_enable to false (defaulting to true for backwards compatibility).

set container network PODNET disable-dns

I've make changes on my forked version of vyos-1x and have tested it to work. I will also submit a PR with the change.