BUG/MINOR: log: t_idle (%Ti) is not set for some requests

BUG/MINOR: log: t_idle (%Ti) is not set for some requests

If TCP content inspection is used, msg_state can be >= HTTP_MSG_ERROR
the first time http_wait_for_request is called. t_idle was being left
unset in that case.

In the example below :
     stick-table type string len 64 size 100k expire 60s
     tcp-request inspect-delay 1s
     tcp-request content track-sc1 hdr(X-Session)

%Ti will always be -1, because the msg_state is already at HTTP_MSG_BODY
when http_wait_for_request is called for the first time.

This patch should backported to 1.8 and 1.7.