Distinct HTTP and HTTPS listen addresses for management HTTP interface are not configurable

Add a single attribute to the existing http management interface resource, named "secure-interface". The current attributes are "interface", "http-port", "https-port", with the "interface" value being used for both ports. The new "secure-interface" attribute would specify the interface to use for the "https-port" socket. It, unlike "interface", will accept a null value, in which case the value for "interface" will be used for the "https-port" socket. This would be the standard config and preserves backward compatibility.