BUG/MEDIUM: h1: Get the h1m state when restarting the headers parsing

BUG/MEDIUM: h1: Get the h1m state when restarting the headers parsing

Since the commit 0f8fb6b7f ("MINOR: h1: make the H1 headers block parser able to
parse headers only"), when headers are not received in one time, a parsing error
is returned because the local state in the function h1_headers_to_hdr_list() was
not initialized with the previous one (in fact, it was not initialized at all).

So now, we start the parsing of headers with the state H1_MSG_HDR_FIRST when the
flag H1_MF_HDRS_ONLY is set. Otherwise, we always get it from the h1m.

This patch must be backported to 1.9.