Unwrap exception more tenaciously in testQueuedOperationsAndBrokenRep…

…oOnMasterFailOver (elastic#102352) (elastic#102367)

There can be more than 10 layers of wrapping RTEs, see elastic#102351. As a
workaround to address the test failure, this commit just manually
unwraps them all.

Closes elastic#102348

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

@@ -39,6 +39,7 @@
 import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.test.disruption.NetworkDisruption;
 import org.elasticsearch.test.transport.MockTransportService;
+import org.elasticsearch.transport.RemoteTransportException;
 
 import java.io.IOException;
 import java.nio.file.Files;
@@ -768,7 +769,18 @@ public void testQueuedOperationsAndBrokenRepoOnMasterFailOver() throws Exception
         ensureStableCluster(3);
 
         awaitNoMoreRunningOperations();
-        expectThrows(RepositoryException.class, deleteFuture::actionGet);
+        var innerException = expectThrows(ExecutionException.class, RuntimeException.class, deleteFuture::get);
+
+        // There may be many layers of RTE to unwrap here, see https://github.com/elastic/elasticsearch/issues/102351.
+        // ExceptionsHelper#unwrapCause gives up at 10 layers of wrapping so we must unwrap more tenaciously by hand here:
+        while (true) {
+            if (innerException instanceof RemoteTransportException remoteTransportException) {
+                innerException = asInstanceOf(RuntimeException.class, remoteTransportException.getCause());
+            } else {
+                assertThat(innerException, instanceOf(RepositoryException.class));
+                break;
+            }
+        }
     }
 
     public void testQueuedSnapshotOperationsAndBrokenRepoOnMasterFailOver() throws Exception {