Always set the DF flag (not only when CMSG is available)

By mistake, we were setting the DF flag only when CMSG was available for
said platform.

lib/isc/unix/socket.c

@@ -2348,8 +2348,6 @@ again:
 #endif /* IPV6_RECVPKTINFO */
 #endif /* defined(USE_CMSG) */
 
-		set_ip_dontfrag(sock);
-
 #if defined(SET_RCVBUF)
 		optlen = sizeof(size);
 		if (getsockopt(sock->fd, SOL_SOCKET, SO_RCVBUF, (void *)&size,
@@ -2416,6 +2414,8 @@ again:
 #endif /* ifdef IP_RECVTOS */
 #endif /* defined(USE_CMSG) || defined(SET_RCVBUF) || defined(SET_SNDBUF) */
 
+	set_ip_dontfrag(sock);
+
 setup_done:
 	inc_stats(manager->stats, sock->statsindex[STATID_OPEN]);
 	if (sock->active == 0) {