Replace Collections.unmodifiableList with guava ImmutableList
diff --git a/core/api/src/main/java/org/onlab/onos/store/service/BatchReadResult.java b/core/api/src/main/java/org/onlab/onos/store/service/BatchReadResult.java
index 525e77f..683ca1c 100644
--- a/core/api/src/main/java/org/onlab/onos/store/service/BatchReadResult.java
+++ b/core/api/src/main/java/org/onlab/onos/store/service/BatchReadResult.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 read operation.
  */
@@ -11,7 +12,7 @@
     private final List<ReadResult> readResults;
 
     public BatchReadResult(List<ReadResult> readResults)  {
-        this.readResults = Collections.unmodifiableList(readResults);
+        this.readResults = ImmutableList.copyOf(readResults);
     }
 
     /**