Transaction fails to set next transaction while the previous one was successfull

2016-03-25 11:40:43,191 | WARN | CommitFutures-3 | PingPongTransactionChain | 118 - org.opendaylight.controller.sal-broker-impl - 1.4.0.SNAPSHOT | Submitting transaction PingPongTransaction

{delegate=org.opendaylight.controller.cluster.databroker.DOMBrokerReadWriteTransaction@54e00608} while PingPongTransaction{delegate=org.opendaylight.controller.cluster.databroker.DOMBrokerReadWriteTransaction@5a27e2e4} is still running
Exception in thread "CommitFutures-2" java.lang.IllegalStateException: Completed transaction PingPongTransaction{delegate=org.opendaylight.controller.cluster.databroker.DOMBrokerReadWriteTransaction@54e00608}

while null was submitted
at com.google.common.base.Preconditions.checkState(Preconditions.java:197)
at org.opendaylight.controller.md.sal.dom.broker.impl.PingPongTransactionChain.processNextTransaction(PingPongTransactionChain.java:212)
at org.opendaylight.controller.md.sal.dom.broker.impl.PingPongTransactionChain.transactionSuccessful(PingPongTransactionChain.java:230)
at org.opendaylight.controller.md.sal.dom.broker.impl.PingPongTransactionChain.access$300(PingPongTransactionChain.java:54)
at org.opendaylight.controller.md.sal.dom.broker.impl.PingPongTransactionChain$2.onSuccess(PingPongTransactionChain.java:200)
at org.opendaylight.controller.md.sal.dom.broker.impl.PingPongTransactionChain$2.onSuccess(PingPongTransactionChain.java:197)
at com.google.common.util.concurrent.Futures$6.run(Futures.java:1319)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

Transaction fails to set next transaction while the previous one was successfull

Steps to reproduce: Compile and run this patch https://git.opendaylight.org/gerrit/#/c/36550/