Update the cassandra example to use a data volume, and a fixed version.

examples/cassandra/image/Dockerfile

@@ -17,5 +17,6 @@ RUN apt-get -qq -y install cassandra
 COPY cassandra.yaml /etc/cassandra/cassandra.yaml
 COPY run.sh /run.sh
 COPY kubernetes-cassandra.jar /kubernetes-cassandra.jar
+RUN chmod a+x /run.sh
 
 CMD /run.sh

examples/cassandra/image/cassandra.yaml

@@ -96,12 +96,12 @@ partitioner: org.apache.cassandra.dht.Murmur3Partitioner
 # the configured compaction strategy.
 # If not set, the default directory is $CASSANDRA_HOME/data/data.
 data_file_directories:
-    - /var/lib/cassandra/data
+    - /cassandra_data/data
 
 # commit log.  when running on magnetic HDD, this should be a
 # separate spindle than the data directories.
 # If not set, the default directory is $CASSANDRA_HOME/data/commitlog.
-commitlog_directory: /var/lib/cassandra/commitlog
+commitlog_directory: /cassandra_data/commitlog
 
 # policy for data disk failures:
 # die: shut down gossip and Thrift and kill the JVM for any fs errors or