MEDIUM: http-htx: Make authority update optional when replacing a header value

MEDIUM: http-htx: Make authority update optional when replacing a header value

When a header value is replaced, a test is performed to verify if the
authority must be updated or not. But there are some places where we know it
is useless. First, when the caller know the header is not the host
header. Then when the host header value is updated because the authority was
changed.

So now, an extra argument was added to http_replace_header() and
http_replace_header_value() functions to specify if the authority update
must be performed or not.