Can be changed with `nfs_v4_only=false` which defaults to true.
Information taken from: https://wiki.debian.org/NFSServerSetup
and applied directly through Ansible.
Currently _irreversible_, meaning once we set the server to v4 only
there is NO ansible-supported playbook to reset it to all NFSv2/3/4
versions.
Has to be done manually, or could be included as manually-run playbook.
