check_dns: unified check output

this also allows us to make tests against "critical" in the output.

Signed-off-by: Sven Nierlein <Sven.Nierlein@consol.de>

plugins/check_dns.c

@@ -154,7 +154,7 @@ main (int argc, char **argv)
       }
 
       if (strcmp(temp_buffer, dns_server) != 0) {
-        die (STATE_CRITICAL, _("No response from DNS %s\n"), dns_server);
+        die (STATE_CRITICAL, _("DNS CRITICAL - No response from DNS %s\n"), dns_server);
       }
     }