Consistently use DOCKER_EXPERIMENTAL=1 instead or =y

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Jenkinsfile

@@ -246,7 +246,7 @@ pipeline {
                                 docker run --rm -t --privileged \
                                   -v "$WORKSPACE/bundles:/go/src/github.com/docker/docker/bundles" \
                                   --name docker-pr$BUILD_NUMBER \
-                                  -e DOCKER_EXPERIMENTAL=y \
+                                  -e DOCKER_EXPERIMENTAL=1 \
                                   -e DOCKER_GITCOMMIT=${GIT_COMMIT} \
                                   -e DOCKER_GRAPHDRIVER \
                                   docker:${GIT_COMMIT}-exp \

hack/ci/experimental

@@ -2,7 +2,7 @@
 # Entrypoint for jenkins experimental CI
 set -eu -o pipefail
 
-export DOCKER_EXPERIMENTAL=y
+export DOCKER_EXPERIMENTAL=1
 
 hack/make.sh \
 	binary-daemon \