SCHEMA-869. C* integration tests should use available ports.

issue: https://jira.kiji.org/browse/SCHEMA-869
review: https://review.kiji.org/r/2043

Use Maven build helper plugin to find available ports.  Assign those
ports to properties in the POM file that correspond to the same
properties for the Cassandra Maven plugin.

Add a file src/test/resources/cassandra-maven-plugin.properties that
also gets the value of the port to use (through resource filtering in
maven).  Update the AbstractCassandraKijiIntegrationTest to use that
properties file to get the appropriate port.