drivers: wifi: esp_at: close stream socket after failure to send

So far send errors were silently ignored. This is okay for
UDP (datagram) sockets, as there is no guarantee that packets will
actually be sent successfully. In case of TCP (stream) stream sockets
however, application layer expects network stack to send requested data
as stream, without losing any part of it.

In case of send errors on stream sockets mark that socket to be closed
and stop sending any subsequent network packets, so that data stream
won't have any holes.

Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>