client: fix response hooks for hijacked requests

Response hooks added in 2bc7febeb6fa ("client: Add HTTP response
hooks") are only installed on the client's HTTP transport.

Hijacked requests use a separate transport and therefore bypass the
configured response hooks.

Wrap the hijack transport with hookTransport so response hooks are
also invoked for the HTTP upgrade response, and add coverage for the
hijack path.

updates 2bc7febeb6fa497cfa4722f6eab8eb46c5c16ba3

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>