Increase the number of connection attempts

In "adb forward" mode, it may take a while before the server socket is
listening, so increase the number of connection attempts.

See <https://github.com/Genymobile/scrcpy/issues/5#issuecomment-373718551>.

app/src/server.c

@@ -199,7 +199,7 @@ socket_t server_connect_to(struct server *server, Uint32 timeout_ms) {
     if (!server->tunnel_forward) {
         server->device_socket = net_accept(server->server_socket);
     } else {
-        Uint32 attempts = 10;
+        Uint32 attempts = 50;
         Uint32 delay = 100; // ms
         server->device_socket = connect_to_server(server->local_port, attempts, delay);
     }