Sonar suggestion - Don't use a mutable collection in a public interface

Change-Id: I6f73f665cff20e558a8ec2f3cd319e4d9b00bb58
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackNetworkManager.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackNetworkManager.java
index 359d34e..76f164f 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackNetworkManager.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackNetworkManager.java
@@ -71,7 +71,7 @@
 import static org.onosproject.net.AnnotationKeys.PORT_NAME;
 import static org.onosproject.openstacknetworking.api.Constants.DIRECT;
 import static org.onosproject.openstacknetworking.api.Constants.PCISLOT;
-import static org.onosproject.openstacknetworking.api.Constants.PORT_NAME_PREFIX_MAP;
+import static org.onosproject.openstacknetworking.api.Constants.portNamePrefixMap;
 import static org.onosproject.openstacknetworking.util.OpenstackNetworkingUtil.getIntfNameFromPciAddress;
 import static org.slf4j.LoggerFactory.getLogger;
 
@@ -339,7 +339,7 @@
     }
 
     private boolean isDirectPort(String portName) {
-        return PORT_NAME_PREFIX_MAP.values().stream().filter(p -> portName.startsWith(p)).findAny().isPresent();
+        return portNamePrefixMap().values().stream().filter(p -> portName.startsWith(p)).findAny().isPresent();
     }
 
     @Override