[test] Avoid running the NoImds test on AWS (elastic#118675)

Disabled the NoImds test on AWS EC2 instance where it fails because the
AWS metadata are available, which is not expected by this test.

plugins/discovery-ec2/src/javaRestTest/java/org/elasticsearch/discovery/ec2/DiscoveryEc2AvailabilityZoneAttributeNoImdsIT.java

@@ -9,6 +9,8 @@
 
 package org.elasticsearch.discovery.ec2;
 
+import com.amazonaws.util.EC2MetadataUtils;
+
 import org.elasticsearch.client.Request;
 import org.elasticsearch.test.cluster.ElasticsearchCluster;
 import org.elasticsearch.test.rest.ESRestTestCase;
@@ -29,6 +31,8 @@ protected String getTestRestCluster() {
     }
 
     public void testAvailabilityZoneAttribute() throws IOException {
+        assumeTrue("test only in non-AWS environment", EC2MetadataUtils.getInstanceId() == null);
+
         final var nodesInfoResponse = assertOKAndCreateObjectPath(client().performRequest(new Request("GET", "/_nodes/_all/_none")));
         for (final var nodeId : nodesInfoResponse.evaluateMapKeys("nodes")) {
             assertNull(nodesInfoResponse.evaluateExact("nodes", nodeId, "attributes", "aws_availability_zone"));