RANGER-5480: fix unit tests failure with error ConcurrentModificationException (apache#837)

Author: mneethiraj

agents-common/src/main/java/org/apache/ranger/plugin/model/RangerBaseModelObject.java

@@ -264,6 +264,10 @@ public static void setNullSafeSupplier(String supplier) {
         }
     }
 
+    public static <T> List<T> copyOrEmpty(List<T> src) {
+        return src == null ? new ArrayList<>() : new ArrayList<>(src);
+    }
+
     public abstract static class NullSafeSupplier {
         public abstract <T> List<T> toList(List<T> coll);
 

agents-common/src/main/java/org/apache/ranger/plugin/model/RangerPolicy.java

@@ -921,7 +921,13 @@ public RangerPolicyItem() {
         }
 
         public RangerPolicyItem(RangerPolicyItem other) {
-            this(other.accesses, other.users, other.groups, other.roles, other.conditions, other.delegateAdmin);
+            this.accesses   = copyOrEmpty(other.accesses);
+            this.users      = copyOrEmpty(other.users);
+            this.groups     = copyOrEmpty(other.groups);
+            this.roles      = copyOrEmpty(other.roles);
+            this.conditions = copyOrEmpty(other.conditions);
+
+            setDelegateAdmin(other.delegateAdmin);
         }
 
         public RangerPolicyItem(List<RangerPolicyItemAccess> accessTypes, List<String> users, List<String> groups, List<String> roles, List<RangerPolicyItemCondition> conditions, Boolean delegateAdmin) {