resolved: when outputting RRs in text form, append a trailing dot to owner names

After all, that's how this is done in DNS, and is particularly important
if we look a DS/DNSKEY RRs for the root zone itself, where the owner
name would otherwise be shown as completely empty (i.e. missing).

src/resolve/resolved-dns-rr.c

@@ -309,7 +309,7 @@ int dns_resource_key_to_string(const DnsResourceKey *key, char **ret) {
                 t = tbuf;
         }
 
-        if (asprintf(&s, "%s %s %-5s", DNS_RESOURCE_KEY_NAME(key), c, t) < 0)
+        if (asprintf(&s, "%s. %s %-5s", DNS_RESOURCE_KEY_NAME(key), c, t) < 0)
                 return -ENOMEM;
 
         *ret = s;