Disable systemd-resolved

Previously, systemd-resolved was installed, but not used.

Starting with systemd-resolved-249.11-1.fc35.x86_64, this changed due to
this change:

> Create /etc/resolv.conf symlink if nothing is present yet (#2032085)

More context in: https://bugzilla.redhat.com/show_bug.cgi?id=2032085

Before this version, resolv.conf was a regular file managed by
NetworkManager.

This commit restores the previous behvaiour by disabling
systemd-resolved, removing /etc/resolv.conf if it is a symlink, and
restarting NetworkManager (so it creates a new resolv.conf).

manifests/public_ip.pp

@@ -17,6 +17,18 @@ class lysnetwork::public_ip (
       ipv6_dns_servers => ['2001:6b0:17:f0a0::4', '2001:6b0:17:f0a0::e1'],
       ipv6_dns_search  => 'lysator.liu.se',
     }
+    # disable systemd-resolved
+    service { 'systemd-resolved':
+      ensure => stopped,
+      enable => false,
+    }
+    -> exec { '/usr/bin/rm -f /etc/resolv.conf':
+      onlyif => '/usr/bin/test -h /etc/resolv.conf',
+    }
+    # avoid managing the service by using an exec resource
+    ~> exec { '/usr/bin/systemctl restart NetworkManager':
+      refreshonly => true,
+    }
   } elsif versioncmp($facts['systemd_version'], '215') >= 0 {
     case $facts['os']['family'] {
       'RedHat': {