Fix looking up the correct image to push to dockerhub

The way we were looking for the image tag to push to dockerhub was
an artifact of how were were pushing to dockerhub in our old conduit
repo. The correct way is demonstrated in this commit, which smacleod
has recommend and is consistent with how it is done in the mozphab repo

Author: purelogiq

circle.yml

@@ -45,5 +45,5 @@ deployment:
     commands:
       - "[ ! -z $DOCKERHUB_REPO ]"
       - docker login -e $DOCKER_EMAIL -u $DOCKER_USER -p $DOCKER_PASS
-      - "docker tag lando-api:build ${DOCKERHUB_REPO}:lando-api-${CIRCLE_SHA1}"
-      - "docker push ${DOCKERHUB_REPO}:lando-api-${CIRCLE_SHA1}"
+      - "docker tag ${DOCKERHUB_REPO} ${DOCKERHUB_REPO}:${CIRCLE_SHA1}"
+      - "docker push ${DOCKERHUB_REPO}:${CIRCLE_SHA1}"