Added an adapter for PersistenceService to be used in unit tests

Change-Id: Ided127f848b97632b021ea1f1c88d912fe28492c
diff --git a/core/store/persistence/src/main/java/org/onosproject/persistence/impl/PersistenceManager.java b/core/store/persistence/src/main/java/org/onosproject/persistence/impl/PersistenceManager.java
index 3428bce..f1ae5f9 100644
--- a/core/store/persistence/src/main/java/org/onosproject/persistence/impl/PersistenceManager.java
+++ b/core/store/persistence/src/main/java/org/onosproject/persistence/impl/PersistenceManager.java
@@ -46,9 +46,8 @@
 @Service
 public class PersistenceManager implements PersistenceService {
 
-    private static final String DATABASE_PATH = "../data/localDB";
-
-    private static final String ENCLOSING_FOLDER = "../data";
+    private static final String DATABASE_PATH = System.getProperty("karaf.data", "./data/localDB");
+    private static final String ENCLOSING_FOLDER = System.getProperty("karaf.data", "./data");
 
     static final String MAP_PREFIX = "map:";