Remove EndpointConfig.Transport from the return value of the
registry.notifications.endpoints expvar.Func. It results in an empty
value for that expvar variable under Go 1.7 because it is a non-nil
*http.Transport, which Go 1.7 can no longer encode as JSON.
Signed-off-by: Noah Treuhaft <noah.treuhaft@docker.com>
(cherry picked from commit 9a58c91051)
