fix issue: #701

Signed-off-by: Xian Chaobo <xianchaobo@huawei.com>

test/integration/api.bats

@@ -43,9 +43,6 @@ function teardown() {
 }
 
 @test "docker attach through websocket" {
-	#FIXME: Broken
-	skip
-
 	CLIENT_API_VERSION="v1.17"
 	start_docker 2
 	swarm_manage
@@ -57,6 +54,8 @@ function teardown() {
 	# jimmyxian/centos7-wssh is an image with websocket CLI(WSSH) wirtten in Nodejs
 	# if connected successfull, it returns two lines, "Session Open" and "Session Closed"
 	# Note: with stdout=1&stdin=1&stream=1: it can be used as SSH
+	docker pull jimmyxian/centos7-wssh
+
 	URL="ws://${SWARM_HOST}/${CLIENT_API_VERSION}/containers/test_container/attach/ws?stderr=1"
 	run docker_host run --rm --net=host jimmyxian/centos7-wssh wssh $URL
 	[ "$status" -eq 0 ]