Update PYTHONPATH (databricks#51)

* Update Dockerfile

* Remove redudant SPARK_HOME

spark/Dockerfile

@@ -32,6 +32,7 @@ RUN curl https://github.com/SpencerPark/IJava/releases/download/v1.3.0/ijava-1.3
 # Optional env variables
 ENV SPARK_HOME=${SPARK_HOME:-"/opt/spark"}
 ENV HADOOP_HOME=${HADOOP_HOME:-"/opt/hadoop"}
+ENV PYTHONPATH=$SPARK_HOME/python:$SPARK_HOME/python/lib/py4j-0.10.9.5-src.zip:$PYTHONPATH
 
 RUN mkdir -p ${HADOOP_HOME} && mkdir -p ${SPARK_HOME}
 WORKDIR ${SPARK_HOME}
@@ -110,7 +111,6 @@ COPY ipython/startup/README /root/.ipython/profile_default/startup
 
 COPY spark-defaults.conf /opt/spark/conf
 ENV PATH="/opt/spark/sbin:/opt/spark/bin:${PATH}"
-ENV SPARK_HOME="/opt/spark"
 
 RUN chmod u+x /opt/spark/sbin/* && \
     chmod u+x /opt/spark/bin/*