[Test] More reliable wait for index to appear (#126437)

Relates: #125652 Resolves: #126204

Author: ywangd

muted-tests.yml

@@ -357,9 +357,6 @@ tests:
 - class: org.elasticsearch.search.basic.SearchWithRandomDisconnectsIT
   method: testSearchWithRandomDisconnects
   issue: https://github.com/elastic/elasticsearch/issues/122707
-- class: org.elasticsearch.snapshots.SharedClusterSnapshotRestoreIT
-  method: testDeletionOfFailingToRecoverIndexShouldStopRestore
-  issue: https://github.com/elastic/elasticsearch/issues/126204
 - class: org.elasticsearch.xpack.esql.inference.RerankOperatorTests
   method: testSimpleCircuitBreaking
   issue: https://github.com/elastic/elasticsearch/issues/124337

server/src/internalClusterTest/java/org/elasticsearch/snapshots/SharedClusterSnapshotRestoreIT.java

@@ -748,7 +748,7 @@ public void testDeletionOfFailingToRecoverIndexShouldStopRestore() throws Except
 
         logger.info("--> wait for the index to appear");
         // that would mean that recovery process started and failing
-        waitForIndex("test-idx", TimeValue.timeValueSeconds(10));
+        safeGet(clusterAdmin().prepareHealth(SAFE_AWAIT_TIMEOUT, "test-idx").execute());
 
         logger.info("--> delete index");
         cluster().wipeIndices("test-idx");
@@ -1619,14 +1619,6 @@ public void testDeleteSnapshotWhileRestoringFails() throws Exception {
         restoreFut.get();
     }
 
-    private void waitForIndex(final String index, TimeValue timeout) throws Exception {
-        assertBusy(
-            () -> assertTrue("Expected index [" + index + "] to exist", indexExists(index)),
-            timeout.millis(),
-            TimeUnit.MILLISECONDS
-        );
-    }
-
     public void testSnapshotName() throws Exception {
         disableRepoConsistencyCheck("This test does not create any data in the repository");