Revert "resolved: demote the global unicast scope"

This commit may have been a breaking change for sd-resolved foreign
resolv.conf mode, where a legacy network management daemon directly
modifies resolv.conf and sd-resolved consumes that.

This reverts commit eded61e410.

man/systemd-resolved.service.xml

@@ -217,10 +217,7 @@
 
       <listitem><para>If a query does not match any configured routing domain (either per-link or global), it
       is sent to all DNS servers that are configured on links with the <varname>DefaultRoute=</varname>
-      option set.</para></listitem>
-
-      <listitem><para>If no links are configured with <varname>DefaultRoute=</varname>, it is sent to the
-      globally configured DNS server.</para></listitem>
+      option set, as well as the globally configured DNS server.</para></listitem>
 
       <listitem><para>If there is no link configured as <varname>DefaultRoute=</varname> and no global DNS
       server configured, one of the compiled-in fallback DNS servers is used.</para></listitem>

src/resolve/resolved-dns-scope.c

@@ -778,8 +778,7 @@ DnsScopeMatch dns_scope_good_domain(
                 if (!dns_scope_is_default_route(s))
                         return DNS_SCOPE_NO;
 
-                /* Prefer suitable per-link scopes where possible */
-                return s->link ? DNS_SCOPE_MAYBE : DNS_SCOPE_LAST_RESORT;
+                return DNS_SCOPE_MAYBE;
         }
 
         case DNS_PROTOCOL_MDNS: {