Clustering : Datastore causes Out Of Memory

To reproduce,

1. Build the OpenFlowPlugin Karaf distribution
2. Run the controller with the following options
JAVA_MAX_MEM=4G JAVA_MAX_PERM_MEM=512m ./karaf
3. Install the odl-mdsal-clustering feature, also install jolokia
4. Run the attached script with the following options
/usr/local/bin/python flow_config_perf.py --nflows 500 --nthreads=5 --ncycles 60

At around 125,000 Transactions the controller will run out of memory