* include/grub/net.h (grub_net_poll_cards): New argument stop_condition.
All users updated.
* grub-core/net/arp.c (have_pending): New var.
(pending_req): Likewise.
(grub_net_arp_send_request): Fill pending_req and use have_pending as
stop indicator.
(grub_net_arp_receive): Set have_pending.
* grub-core/net/dns.c (recv_data): New field stop.
(recv_hook): Set stop.
(grub_net_dns_lookup): Init stop and use as stop condition.
* grub-core/net/http.c (http_establish): Use headers_recv as stop
condition.
* grub-core/net/net.c (grub_net_poll_cards): New argument
stop_condition. Stop when it goes true.
* grub-core/net/tcp.c (grub_net_tcp_open): Use `established' as stop
indicator.
* grub-core/net/tftp.c (tftp_open): Use `have_oack' as stop indicator.
