Mark shutdown non-master nodes test as awaits fix

This commit marks a failing test as awaits fix. The test is failing due
to a primary shard not knowing its own local checkpoint in the global
checkpoint tracker after recovery. If such a shard becomes primary after
promotion, and is then subsequently relocated, it can lead to a
violation of an assertion that when the primary context is transferred
the knowledge of all in-sync local checkpoints is consistent with the
global checkpoint on the relocation target.

Relates #25415

core/src/test/java/org/elasticsearch/cluster/MinimumMasterNodesIT.java

@@ -188,6 +188,7 @@ public class MinimumMasterNodesIT extends ESIntegTestCase {
         }
     }
 
+    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/25415")
     public void testMultipleNodesShutdownNonMasterNodes() throws Exception {
         Settings settings = Settings.builder()
                 .put("discovery.zen.minimum_master_nodes", 3)