test/with_api_v1: delete duplicate close of http body.
test/with_api_v1: delete duplicate close of http body.

Signed-off-by: johncming <64aa7c399bffb85fffaccf95be9acb9553c38de5@yahoo.com>

prometheus/alertmanager,GoogleCloudPlatform/alertmanager,prometheus/alertmanager,prometheus/alertmanager,GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager,prometheus/alertmanager