Improved handling of connection refused in do_sync_query().

Rev: lib/modules/Protocols.pmod/DNS.pmod:1.41

lib/modules/Protocols.pmod/DNS.pmod

@@ -563,6 +563,8 @@ class client
       udp->send(nameservers[i % sizeof(nameservers)], 53, s);
 
       while (udp->wait(RETRY_DELAY)) {
+	// udp->read() can throw an error on connection refused.
+	catch {
 	  m = udp->read();
 	  if ((m->port == 53) &&
 	      (m->data[0..1] == s[0..1]) &&
@@ -570,6 +572,7 @@ class client
 	    // Success.
 	    return decode_res(m->data);
 	  }
+	};
       }
     }
     // Failure.