### CI Link

https://gradle-enterprise.elastic.co/s/7dleq35dp5stm

### Repro line

./gradlew ':x-pack:plugin:core:test' --tests "org.elasticsearch.xpack.core.ilm.SetSingleNodeAllocateStepTests.testPerformActionAttrsRequestFails" -Dtests.seed=6B438F3C3DADE5D2 -Dtests.locale=nl -Dtests.timezone=Asia/Chongqin

### Does it reproduce?

Yes

### Applicable branches

8.1, 8.0

### Failure history

Seems to fail rarely, but has failed before. Example: https://gradle-enterprise.elastic.co/s/d33b4fzn7yoh6

### Failure excerpt

```
org.elasticsearch.xpack.core.ilm.SetSingleNodeAllocateStepTests > testPerformActionAttrsRequestFails FAILED
    java.lang.AssertionError: Node roles must not be provided as attributes but saw attributes {ml=K}
        at __randomizedtesting.SeedInfo.seed([C679BACC1DA27FA7:CB16887322D9C088]:0)
        at org.elasticsearch.cluster.node.DiscoveryNode.<init>(DiscoveryNode.java:233)
        at org.elasticsearch.cluster.node.DiscoveryNode.<init>(DiscoveryNode.java:175)
```
x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ilm/SetSingleNodeAllocateStepTests.java
public void testPerformActionAttrsAllNodesValid() throws Exception {
        int numAttrs = randomIntBetween(1, 10);
        final int numNodes = randomIntBetween(1, 20);
        String[][] validAttrs = new String[numAttrs][2];
        for (int i = 0; i < numAttrs; i++) {
            validAttrs[i] = new String[] { randomAlphaOfLengthBetween(1, 20), randomAlphaOfLengthBetween(1, 20) };
        }
        Settings.Builder indexSettings = settings(Version.CURRENT);
        for (String[] attr : validAttrs) {
            indexSettings.put(IndexMetadata.INDEX_ROUTING_INCLUDE_GROUP_SETTING.getKey() + attr[0], attr[1]);
        }
        IndexMetadata indexMetadata = IndexMetadata.builder(randomAlphaOfLength(10))
            .settings(indexSettings)
            .numberOfShards(randomIntBetween(1, 5))
            .numberOfReplicas(randomIntBetween(0, numNodes - 1))
            .build();
        Index index = indexMetadata.getIndex();
        Set<String> validNodeIds = new HashSet<>();
        Settings validNodeSettings = Settings.EMPTY;
        DiscoveryNodes.Builder nodes = DiscoveryNodes.builder();
        for (int i = 0; i < numNodes; i++) {
            String nodeId = "node_id_" + i;
            String nodeName = "node_" + i;
            int nodePort = 9300 + i;
            String[] nodeAttr = randomFrom(validAttrs);
            Settings nodeSettings = Settings.builder()
                .put(validNodeSettings)
                .put(Node.NODE_NAME_SETTING.getKey(), nodeName)
                .put(Node.NODE_ATTRIBUTES.getKey() + nodeAttr[0], nodeAttr[1])
                .build();