Prevent the rolling upgrades rest tests from cleaning up indices

after finishing if a the tests.rest.preserve_indices system property
is set

qa/rolling-upgrade/build.gradle

@@ -31,6 +31,7 @@ task oldClusterTest(type: RestIntegTestTask) {
     clusterName = 'rolling-upgrade'
   }
   systemProperty 'tests.rest.suite', 'old_cluster'
+  systemProperty 'tests.rest.preserve_indices', 'true'
 }
 
 task mixedClusterTest(type: RestIntegTestTask) {
@@ -42,7 +43,7 @@ task mixedClusterTest(type: RestIntegTestTask) {
     dataDir = "${-> oldClusterTest.nodes[1].dataDir}"
   }
   systemProperty 'tests.rest.suite', 'mixed_cluster'
-
+  systemProperty 'tests.rest.preserve_indices', 'true'
 }
 
 task upgradedClusterTest(type: RestIntegTestTask) {

qa/rolling-upgrade/src/test/resources/rest-api-spec/test/mixed_cluster/10_basic.yaml

@@ -1,5 +1,15 @@
 ---
 "Index data and search on the mixed cluster":
+ - do:
+     cluster.health:
+        wait_for_status: green
+
+ - do:
+      indices.get_settings:
+        index: test_index
+
+ - match: { test_index.settings.index.number_of_replicas: "0" }
+
  - do:
      search:
         index: test_index

qa/rolling-upgrade/src/test/resources/rest-api-spec/test/old_cluster/10_basic.yaml

@@ -1,5 +1,13 @@
 ---
 "Index data and search on the old cluster":
+ - do:
+     indices.create:
+        index: test_index
+        body:
+          settings:
+            index:
+              number_of_replicas: 0
+
  - do:
      bulk:
         refresh: true

qa/rolling-upgrade/src/test/resources/rest-api-spec/test/upgraded_cluster/10_basic.yaml

@@ -1,5 +1,9 @@
 ---
 "Index data and search on the upgraded cluster":
+ - do:
+     cluster.health:
+        wait_for_status: green
+
  - do:
      search:
        index: test_index

test/framework/src/main/java/org/elasticsearch/test/rest/ESRestTestCase.java

@@ -138,13 +138,16 @@ public class ESRestTestCase extends ESTestCase {
     }
 
     private void wipeCluster() throws IOException {
-        // wipe indices
-        try {
-            adminClient().performRequest("DELETE", "*");
-        } catch (ResponseException e) {
-            // 404 here just means we had no indexes
-            if (e.getResponse().getStatusLine().getStatusCode() != 404) {
-                throw e;
+        final boolean preserveIndices = Boolean.parseBoolean(System.getProperty("tests.rest.preserve_indices"));
+        if (preserveIndices == false) {
+            // wipe indices
+            try {
+                adminClient().performRequest("DELETE", "*");
+            } catch (ResponseException e) {
+                // 404 here just means we had no indexes
+                if (e.getResponse().getStatusLine().getStatusCode() != 404) {
+                    throw e;
+                }
             }
         }