add -a switch to push all tags per docker/cli#2220 (#330)

Author: mlabardini-opti

scripts/ci_upload_packages.sh

@@ -6,8 +6,10 @@ if [[ $TRAVIS_OS_NAME == "linux" ]]; then
 
   # push docker images to dockerhub
   echo "$DOCKERHUB_PASS" | docker login -u "$DOCKERHUB_USER" --password-stdin
-  # if you dont specify the tag, it'll push all image versions
-  docker push optimizely/agent
+  # if you dont specify the tag, it'll push all image versions --> No longer the default
+  # https://docs.docker.com/engine/release-notes/#20100
+  # Add -a/--all-tags to docker push docker/cli#2220
+  docker push -a optimizely/agent
 
 elif [[ $TRAVIS_OS_NAME == "osx" ]]; then
   echo "we're on osx"