[ML][TEST] Fix NPE in JobManagerTests

Author: davidkyle

x-pack/plugin/ml/src/test/java/org/elasticsearch/xpack/ml/job/persistence/MockClientBuilder.java

@@ -283,6 +283,7 @@ public MockClientBuilder prepareSearch(String indexName, List<BytesReference> do
         when(builder.setIndicesOptions(any())).thenReturn(builder);
         when(builder.setQuery(any())).thenReturn(builder);
         when(builder.setSource(any())).thenReturn(builder);
+        when(builder.setSize(anyInt())).thenReturn(builder);
         SearchRequest request = new SearchRequest(indexName);
         when(builder.request()).thenReturn(request);
 
@@ -321,6 +322,7 @@ public MockClientBuilder prepareSearchFields(String indexName, List<Map<String,
         when(builder.setIndicesOptions(any())).thenReturn(builder);
         when(builder.setQuery(any())).thenReturn(builder);
         when(builder.setSource(any())).thenReturn(builder);
+        when(builder.setSize(anyInt())).thenReturn(builder);
         SearchRequest request = new SearchRequest(indexName);
         when(builder.request()).thenReturn(request);