This is where we need a superset of the HEAD responses.  The head response structure is initialized prior to issuing the HEAD request.  The head response gets populated with the results.  We want to maintain the content range header results from first HEAD request and update with the time seek header fields from second request.   I chose to have the head_response represent the results from a single HEAD request and then have logic to update the server_info and maintain the super set of the results from all HEAD requests.