Missed an && (#587)

Author: coderanger

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

@@ -23,7 +23,7 @@ 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 && \
     touch /opt/spark/RELEASE && \
     rm /bin/sh && \
     ln -sv /bin/bash /bin/sh && \