extend keep alive interval to 100%

MQTT Specifications allows client a time of one and a half time the keep alive interval before sending the next control packet to keep the connection alive.
> "If the Keep Alive value is non-zero and the Server does not receive a Control Packet from the Client within one and a half times the Keep Alive time period, it MUST disconnect the Network Connection to the Client as if the network had failed."

Author: luffykesh

src/lwmqtt/client.c

@@ -357,8 +357,8 @@ lwmqtt_err_t lwmqtt_connect(lwmqtt_client_t *client, lwmqtt_options_t options, l
   // set command timer
   client->timer_set(client->command_timer, timeout);
 
-  // save keep alive interval (take 75% to be a little earlier than actually needed)
-  client->keep_alive_interval = (uint32_t)(options.keep_alive) * 750;
+  // save keep alive interval
+  client->keep_alive_interval = (uint32_t)(options.keep_alive) * 1000;
 
   // set keep alive timer
   client->timer_set(client->keep_alive_timer, client->keep_alive_interval);