build.sh: Consistently add ${DOCKER_SUFFIX} for images built

This follows the change previously done to bionic-amd64-tf-m-build,
and will allow to properly namespace sanity-check images and preclude
them leaking into production image namespace (TFC-220).

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I1fdfac7d9ba7f320eac91a1a9a63277f85d96c7d
diff --git a/alpine-amd64-node10-tf-a/build.sh b/alpine-amd64-node10-tf-a/build.sh
index e876f5e..3ec158a 100755
--- a/alpine-amd64-node10-tf-a/build.sh
+++ b/alpine-amd64-node10-tf-a/build.sh
@@ -4,6 +4,6 @@
 
 export LANG=C
 
-image=trustedfirmware/ci-node-tf-a-alpine:alpine10
+image=trustedfirmware/ci-node-tf-a-alpine:alpine10${DOCKER_SUFFIX}
 docker build --pull --tag=$image .
 echo $image > .docker-tag