Don't pass feature flag to non-snapshot artifacts (#80033)

When configuring BWC tests to use feature flags, we need to ensure we
don't inadvertently enable the flag on the old version nodes, as those
are NOT release builds and therefore fail if the feature flag is
present. This commit tweaks our config here to ensure we explicitly
enable the flag only on the upgraded nodes. Closes #78219

qa/full-cluster-restart/build.gradle

@@ -23,7 +23,7 @@ BuildParams.bwcVersions.withIndexCompatiple { bwcVersion, baseName ->
       setting 'indices.memory.shard_inactive_time', '60m'
       setting 'path.repo', "${buildDir}/cluster/shared/repo/${baseName}"
       setting 'xpack.security.enabled', 'false'
-      if (BuildParams.isSnapshotBuild() == false) {
+      if (BuildParams.isSnapshotBuild() == false && bwcVersion.toString() == project.version) {
         systemProperty 'es.index_mode_feature_flag_registered', 'true'
       }
   }
@@ -42,6 +42,9 @@ BuildParams.bwcVersions.withIndexCompatiple { bwcVersion, baseName ->
     useCluster baseCluster
     dependsOn "${baseName}#oldClusterTest"
     doFirst {
+      if (BuildParams.isSnapshotBuild() == false) {
+        baseCluster.get().systemProperty 'es.index_mode_feature_flag_registered', 'true'
+      }
       baseCluster.get().goToNextVersion()
     }
     systemProperty 'tests.is_old_cluster', 'false'

qa/rolling-upgrade/build.gradle

@@ -36,6 +36,9 @@ BuildParams.bwcVersions.withWireCompatiple { bwcVersion, baseName ->
     setting 'repositories.url.allowed_urls', 'http://snapshot.test*'
     setting 'path.repo', "${buildDir}/cluster/shared/repo/${baseName}"
     setting 'xpack.security.enabled', 'false'
+    if (BuildParams.isSnapshotBuild() == false && bwcVersion.toString() == project.version) {
+      systemProperty 'es.index_mode_feature_flag_registered', 'true'
+    }
   }
 
   String oldVersion = bwcVersion.toString()
@@ -57,6 +60,9 @@ BuildParams.bwcVersions.withWireCompatiple { bwcVersion, baseName ->
     dependsOn "${baseName}#oldClusterTest"
     useCluster baseCluster
     doFirst {
+      if (BuildParams.isSnapshotBuild() == false) {
+        baseCluster.get().nodes."${baseName}-0".systemProperty 'es.index_mode_feature_flag_registered', 'true'
+      }
       baseCluster.get().nextNodeToNextVersion()
     }
     systemProperty 'tests.rest.suite', 'mixed_cluster'
@@ -70,6 +76,9 @@ BuildParams.bwcVersions.withWireCompatiple { bwcVersion, baseName ->
     dependsOn "${baseName}#oneThirdUpgradedTest"
     useCluster baseCluster
     doFirst {
+      if (BuildParams.isSnapshotBuild() == false) {
+        baseCluster.get().nodes."${baseName}-1".systemProperty 'es.index_mode_feature_flag_registered', 'true'
+      }
       baseCluster.get().nextNodeToNextVersion()
     }
     systemProperty 'tests.rest.suite', 'mixed_cluster'
@@ -82,6 +91,9 @@ BuildParams.bwcVersions.withWireCompatiple { bwcVersion, baseName ->
   tasks.register("${baseName}#upgradedClusterTest", StandaloneRestIntegTestTask) {
     dependsOn "${baseName}#twoThirdsUpgradedTest"
     doFirst {
+      if (BuildParams.isSnapshotBuild() == false) {
+        baseCluster.get().nodes."${baseName}-2".systemProperty 'es.index_mode_feature_flag_registered', 'true'
+      }
       baseCluster.get().nextNodeToNextVersion()
     }
     useCluster testClusters.named(baseName)
@@ -95,9 +107,3 @@ BuildParams.bwcVersions.withWireCompatiple { bwcVersion, baseName ->
     dependsOn tasks.named("${baseName}#upgradedClusterTest")
   }
 }
-
-testClusters.configureEach {
-  if (BuildParams.isSnapshotBuild() == false) {
-    systemProperty 'es.index_mode_feature_flag_registered', 'true'
-  }
-}

x-pack/qa/full-cluster-restart/build.gradle

@@ -55,7 +55,7 @@ BuildParams.bwcVersions.withIndexCompatiple { bwcVersion, baseName ->
         keystore 'xpack.security.transport.ssl.secure_key_passphrase', 'testnode'
 
         setting 'xpack.security.authc.api_key.enabled', 'true'
-        if (BuildParams.isSnapshotBuild() == false) {
+        if (BuildParams.isSnapshotBuild() == false && bwcVersion.toString() == project.version) {
             systemProperty 'es.index_mode_feature_flag_registered', 'true'
         }
     }
@@ -78,6 +78,9 @@ BuildParams.bwcVersions.withIndexCompatiple { bwcVersion, baseName ->
         useCluster baseCluster
         dependsOn "${baseName}#oldClusterTest"
         doFirst {
+            if (BuildParams.isSnapshotBuild() == false) {
+                systemProperty 'es.index_mode_feature_flag_registered', 'true'
+            }
             testClusters.named(baseName).get().goToNextVersion()
         }
         systemProperty 'tests.is_old_cluster', 'false'