Refactor: perform further code simplification using asJavaMap

Change-Id: If61d9a0c14f77768a902c8c18340733bfb5d5357
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/DistributedSecurityGroupStore.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/DistributedSecurityGroupStore.java
index c82c703..0e1a880 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/DistributedSecurityGroupStore.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/DistributedSecurityGroupStore.java
@@ -50,7 +50,10 @@
 import static java.util.concurrent.Executors.newSingleThreadExecutor;
 import static org.onlab.util.Tools.groupedThreads;
 import static org.onosproject.openstacknetworking.api.Constants.OPENSTACK_NETWORKING_APP_ID;
-import static org.onosproject.openstacknetworking.api.OpenstackSecurityGroupEvent.Type.*;
+import static org.onosproject.openstacknetworking.api.OpenstackSecurityGroupEvent.Type.OPENSTACK_SECURITY_GROUP_CREATED;
+import static org.onosproject.openstacknetworking.api.OpenstackSecurityGroupEvent.Type.OPENSTACK_SECURITY_GROUP_REMOVED;
+import static org.onosproject.openstacknetworking.api.OpenstackSecurityGroupEvent.Type.OPENSTACK_SECURITY_GROUP_RULE_CREATED;
+import static org.onosproject.openstacknetworking.api.OpenstackSecurityGroupEvent.Type.OPENSTACK_SECURITY_GROUP_RULE_REMOVED;
 import static org.slf4j.LoggerFactory.getLogger;
 
 /**
@@ -138,16 +141,12 @@
 
     @Override
     public SecurityGroup securityGroup(String sgId) {
-        Versioned<SecurityGroup> osSg = osSecurityGroupStore.get(sgId);
-        return osSg == null ? null : osSg.value();
+        return osSecurityGroupStore.asJavaMap().get(sgId);
     }
 
     @Override
     public Set<SecurityGroup> securityGroups() {
-        Set<SecurityGroup> osSgs = osSecurityGroupStore.values().stream()
-                .map(Versioned::value)
-                .collect(Collectors.toSet());
-        return ImmutableSet.copyOf(osSgs);
+        return ImmutableSet.copyOf(osSecurityGroupStore.asJavaMap().values());
     }
 
     @Override