fix #538 - make /opt/spark/work-dir writable by gid 0 to operate better in anonymous uid scenarios

Author: erikerlandson

resource-managers/kubernetes/docker-minimal-bundle/src/main/docker/spark-base/Dockerfile

@@ -23,7 +23,8 @@ FROM openjdk:8-alpine
 RUN apk upgrade --no-cache && \
     apk add --no-cache bash tini && \
     mkdir -p /opt/spark && \
-    mkdir -p /opt/spark/work-dir \
+    mkdir -p /opt/spark/work-dir && \
+    chgrp -R root /opt/spark/work-dir && chmod -R ug+rwX /opt/spark/work-dir && \
     touch /opt/spark/RELEASE && \
     rm /bin/sh && \
     ln -sv /bin/bash /bin/sh && \