fix-host-header-contents--introduce-canonical-hostname-api.patch

I?aki pointed out the dummy host field used in client test and ping
is not valid http.  This patch changes it to use the actual host
name and adds an api to collect that from the context cheaply.

Reported-by: I?aki Baz Castillo <ibc@aliax.net>
Signed-off-by: Andy Green <andy@warmcat.com>