def exec_api(json_req)
      begin
        req = sign_request(json_req)
        return HttpChannel.new(api_uri).execute(req)
      rescue Curl::Err::CurlError => ex
        return JsonResponse.new("fail", ex.message)
      end
    end
def exec_api(json_req)
      begin
        req = sign_request(json_req)
        return HttpChannel.new(api_uri).execute(req)
      rescue Curl::Err::CurlError => ex
        return JsonResponse.new("fail", ex.message)
      end
    end
Execute the given API request on the manager

 @param [JsonRequest] json_req
 @return [JsonResponse]