BUG/MINOR: httpclient: use a placeholder value for Host header

A Host header must be present for http_update_host() to success.
htx_add_header(htx, ist("Host"), IST_NULL) was used but this is not a
good idea from a semantic point of view. It also tries to make a memcpy
with a len of 0, which is unrequired.

Use an ist("h") instead as a placeholder value.

This patch fixes bug #1439.
1 file changed