Fix bwc tests failure to extract (#39619)

* Set correct packaging for older versions

Continue using zip packages for pre 7
Some other bwc fixes that hid behind this one.
Closes #39441  #39751

buildSrc/src/main/groovy/org/elasticsearch/gradle/test/ClusterFormationTasks.groovy

@@ -194,7 +194,7 @@ class ClusterFormationTasks {
         }
         Version version = Version.fromString(elasticsearchVersion)
         String os = getOs()
-        String classifier = "${os}-x86_64"
+        String classifier = "-${os}-x86_64"
         String packaging = os.equals('windows') ? 'zip' : 'tar.gz'
         String artifactName = 'elasticsearch'
         if (distro.equals('oss') && Version.fromString(elasticsearchVersion).onOrAfter('6.3.0')) {
@@ -204,6 +204,7 @@ class ClusterFormationTasks {
         String snapshotProject = "${os}-${os.equals('windows') ? 'zip' : 'tar'}"
         if (version.before("7.0.0")) {
             snapshotProject = "zip"
+            packaging = "zip"
         }
         if (distro.equals("oss")) {
             snapshotProject = "oss-" + snapshotProject
@@ -224,7 +225,7 @@ class ClusterFormationTasks {
                 classifier = "" // for bwc, before we had classifiers
             }
             // group does not matter as it is not used when we pull from the ivy repo that points to the download service
-            dependency = "dnm:${artifactName}:${elasticsearchVersion}-${classifier}@${packaging}"
+            dependency = "dnm:${artifactName}:${elasticsearchVersion}${classifier}@${packaging}"
         }
         project.dependencies.add(configuration.name, dependency)
     }

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

@@ -294,7 +294,10 @@ public abstract class ESRestTestCase extends ESTestCase {
     @After
     public final void cleanUpCluster() throws Exception {
         if (preserveClusterUponCompletion() == false) {
-            ensureNoInitializingShards();
+            if (nodeVersions.stream().noneMatch(version -> version.before(Version.V_6_2_0))) {
+                // wait_for_no_initializing_shards added in 6.2
+                ensureNoInitializingShards();
+            }
             wipeCluster();
             waitForClusterStateUpdatesToFinish();
             logIfThereAreRunningTasks();