Pbuf leak if call close before recv complete

[kyliuxing]

Hi,
I met a Pbuf leak issue.
when i call mbed_lwip_socket_recv(), if the parameter size is smaller than pbuf's payload(or interrupt by someone), i can't get all data in once. but if i close the socket after that immediatly, nobody will release that pbuf.
So should we call netbuf_delete() in mbed_lwip_socket_close to check it?

Thanks!

RDA shileiyu

[0xc0170]

cc @kjbracey-arm @geky

[kjbracey]

You're right, mbed_lwip_socket_close should be freeing s->buf.

I'll submit a PR.

[sg-]

Fixed with #3975