Exception found in karaf log when deleting neutron port which was created on subnet using openstack commands

Production steps:

1) Create NET/SUBNET

2) Create VM on SUBNET

3) create port on SUBNET

openstack port create --fixed-ip subnet=SUBNET,ip-address=10.100.5.3 --network NET port53

4) Delete port

openstack port delete  port53

The following Exception observed in karaf log:

2017-12-14 15:22:35,629 | INFO  | eChangeHandler-0 | SubnetOpDpnManager               | 332 - org.opendaylight.netvirt.vpnmanager-impl - 0.5.1 | removePortOpDataEntry: Cannot delete, portOp for port 4eb32b18-1ec3-45db-9e22-ba5d3fc6c69d is not available in datastore
2017-12-14 15:22:35,653 | WARN  | nPool-1-worker-1 | InterfaceConfigListener          | 239 - org.opendaylight.genius.interfacemanager-impl - 0.3.1 | parent refs not specified for 4eb32b18-1ec3-45db-9e22-ba5d3fc6c69d
2017-12-14 15:22:35,658 | WARN  | nPool-1-worker-0 | MDSALManager                     | 246 - org.opendaylight.genius.mdsalutil-impl - 0.3.1 | Flow FlowKey [_id=Uri [_value=Acl_Filter_Ingress_10.100.5.3_5002]] does not exist for dpn 8796749933817
2017-12-14 15:22:35,658 | ERROR | eChangeHandler-0 | AsyncDataTreeChangeListenerBase  | 245 - org.opendaylight.genius.mdsalutil-api - 0.3.1 | Thread terminated due to uncaught exception: AsyncDataTreeChangeListenerBase-DataTreeChangeHandler-0
java.lang.NullPointerException
        at org.opendaylight.netvirt.aclservice.AbstractAclServiceImpl.syncRemoteAclTableFromOtherDpns(AbstractAclServiceImpl.java:468)[302:org.opendaylight.netvirt.aclservice-impl:0.5.1]
        at org.opendaylight.netvirt.aclservice.AbstractAclServiceImpl.updateRemoteAclFilterTable(AbstractAclServiceImpl.java:448)[302:org.opendaylight.netvirt.aclservice-impl:0.5.1]
        at org.opendaylight.netvirt.aclservice.AbstractAclServiceImpl.updateRemoteAclFilterTable(AbstractAclServiceImpl.java:424)[302:org.opendaylight.netvirt.aclservice-impl:0.5.1]
        at org.opendaylight.netvirt.aclservice.AbstractAclServiceImpl.unbindAcl(AbstractAclServiceImpl.java:120)[302:org.opendaylight.netvirt.aclservice-impl:0.5.1]
        at org.opendaylight.netvirt.aclservice.AclServiceManagerImpl.notify(AclServiceManagerImpl.java:66)[302:org.opendaylight.netvirt.aclservice-impl:0.5.1]
        at org.opendaylight.netvirt.aclservice.listeners.AclInterfaceListener.remove(AclInterfaceListener.java:76)[302:org.opendaylight.netvirt.aclservice-impl:0.5.1]
        at org.opendaylight.netvirt.aclservice.listeners.AclInterfaceListener.remove(AclInterfaceListener.java:34)[302:org.opendaylight.netvirt.aclservice-impl:0.5.1]
        at org.opendaylight.genius.datastoreutils.AsyncDataTreeChangeListenerBase$DataTreeChangeHandler.run(AsyncDataTreeChangeListenerBase.java:150)[245:org.opendaylight.genius.mdsalutil-api:0.3.1]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)[:1.8.0_151]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)[:1.8.0_151]
        at java.lang.Thread.run(Thread.java:748)[:1.8.0_151]
2017-12-14 15:22:35,658 | WARN  | nPool-1-worker-0 | MDSALManager                     | 246 - org.opendaylight.genius.mdsalutil-impl - 0.3.1 | Flow FlowKey [_id=Uri [_value=Acl_Filter_Ingress_fe80:0:0:0:f816:3eff:fe86:8786_5002]] does not exist for dpn 8796749933817
2017-12-14 15:22:35,687 | INFO  | n-dispatcher-162 | FlowBasedServicesConfigListener  | 239 - org.opendaylight.genius.interfacemanager-impl - 0.3.1 | Service Binding Entry removed for Interface: 4eb32b18-1ec3-45db-9e22-ba5d3fc6c69d, Data: BoundServices{getServiceName=acl.ingressacl.4eb32b18-1ec3-45db-9e22-ba5d3fc6c69d, getServicePriority=6, getServiceType=class org.opendaylight.yang.gen.v1.urn.opendaylight.genius.interfacemanager.servicebinding.rev160406.ServiceTypeFlowBased, augmentations={interface org.opendaylight.yang.gen.v1.urn.opendaylight.genius.interfacemanager.servicebinding.rev160406.StypeOpenflow=StypeOpenflow{getFlowCookie=110100480, getFlowPriority=1, getInstruction=[Instruction{getInstruction=WriteMetadataCase{getWriteMetadata=WriteMetadata{getMetadata=83919634432, getMetadataMask=1099494850560, augmentations={}}, augmentations={}}, getOrder=1, augmentations={}}, Instruction\{getInstruction=GoToTableCase{getGoToTable=GoToTable{getTableId=239, augmentations={}}, augmentations={}}, getOrder=2, augmentations={}}]}}}