nameserver checks handling rework
We can see various defaults with NetworkManager and dns resolvers. RHEL8 and older Fedoras (32 and older) all use glibc's resolver which is using /etc/resolv.conf file.
In Fedora 33 the default is set to systemd-resolvd and glibc resolver is communicating with it on localhost. Thus a link from /etc/resolv.conf to /run/systemd/resolve/stub-resolv.conf.
We can use resolvectl binary to see per device configurations. Some options are not valid for resolved so these tests are marked @not_with_systemd_resolved these that do need resolved are marked @dns_systemd_resolved
Nameserver checks are now handled in different step which can handle both resolved/glibc resolvers and can handle domains as well as Nameservers.
We have some bugs revealed:
Edited by Vladimír Beneš