[test] fix compilation warning

src/kudu/integration-tests/flex_partitioning-itest.cc:221:32: warning: loop variable 'split' of type 'const vector<int32_t>' (aka 'const vector<int>') creates a copy from type 'const vector<int32_t>' [-Wrange-loop-construct]
    for (const vector<int32_t> split : range_partition.splits) {
                               ^

Change-Id: I16ab253ab99808c2a69b0520a3a6b6253f27f2f8
Reviewed-on: http://gerrit.cloudera.org:8080/16766
Reviewed-by: Grant Henke <granthenke@apache.org>
Tested-by: Grant Henke <granthenke@apache.org>
diff --git a/src/kudu/integration-tests/flex_partitioning-itest.cc b/src/kudu/integration-tests/flex_partitioning-itest.cc
index 4f6cca2..6da3b1f 100644
--- a/src/kudu/integration-tests/flex_partitioning-itest.cc
+++ b/src/kudu/integration-tests/flex_partitioning-itest.cc
@@ -218,7 +218,7 @@
     }
 
     vector<const KuduPartialRow*> split_rows;
-    for (const vector<int32_t> split : range_partition.splits) {
+    for (const auto& split : range_partition.splits) {
       KuduPartialRow* row = schema.NewRow();
       for (int i = 0; i < split.size(); i++) {
         ASSERT_OK(row->SetInt32(range_partition.columns[i], split[i]));