Replace Collections.unmodifiableList with guava ImmutableList
diff --git a/core/api/src/main/java/org/onlab/onos/store/service/BatchWriteResult.java b/core/api/src/main/java/org/onlab/onos/store/service/BatchWriteResult.java
index 4e1848b..b185072 100644
--- a/core/api/src/main/java/org/onlab/onos/store/service/BatchWriteResult.java
+++ b/core/api/src/main/java/org/onlab/onos/store/service/BatchWriteResult.java
@@ -1,8 +1,9 @@
 package org.onlab.onos.store.service;
 
-import java.util.Collections;
 import java.util.List;
 
+import com.google.common.collect.ImmutableList;
+
 /**
  * Result of a batch write operation.
  */
@@ -11,7 +12,7 @@
     private final List<WriteResult> writeResults;
 
     public BatchWriteResult(List<WriteResult> writeResults) {
-        this.writeResults = Collections.unmodifiableList(writeResults);
+        this.writeResults = ImmutableList.copyOf(writeResults);
     }
 
     /**