httpd: make rmt_ip variable local

httpd: make rmt_ip variable local

function                                             old     new   delta
handle_incoming_and_exit                            2385    2398     +13
if_ip_denied_send_HTTP_FORBIDDEN_and_exit             51      54      +3
get_line                                             110     106      -4
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(add/remove: 0/0 grow/shrink: 2/1 up/down: 16/-4)              Total: 12 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>