The pipeline defined in the bulk update item here is ignored:

```
POST /_bulk
{"update":{"_id":"1","_index":"pipeline-test","pipeline":"lowercase-pipeline"}}
{"upsert":{"myField":"UPPER"},"script":{"source":"ctx._source.myField = 'CHANGED'","lang":"painless"}}
```

Only if the pipeline is defined as query string argument, then the pipeline is picked up and used to process the upset:

```
POST /_bulk?pipeline=lowercase-pipeline
{"update":{"_id":"1","_index":"pipeline-test"}}
{"upsert":{"myField":"UPPER"},"script":{"source":"ctx._source.myField = 'CHANGED'","lang":"painless"}}
```

The Bulk API should also use the pipeline defined in the bulk update item.
server/src/main/java/org/elasticsearch/action/bulk/BulkRequestParser.java
import org.elasticsearch.action.index.IndexRequest;
import org.elasticsearch.action.update.UpdateRequest;
import org.elasticsearch.common.bytes.BytesReference;
import org.elasticsearch.common.logging.DeprecationLogger;
import org.elasticsearch.common.lucene.uid.Versions;
import org.elasticsearch.common.xcontent.LoggingDeprecationHandler;
import org.elasticsearch.core.Nullable;
import org.elasticsearch.core.RestApiVersion;
import org.elasticsearch.index.VersionType;
import org.elasticsearch.index.seqno.SequenceNumbers;
import org.elasticsearch.rest.action.document.RestBulkAction;
import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
import org.elasticsearch.xcontent.ParseField;
import org.elasticsearch.xcontent.XContent;
import org.elasticsearch.xcontent.XContentEOFException;
import org.elasticsearch.xcontent.XContentParser;
import org.elasticsearch.xcontent.XContentParserConfiguration;
import org.elasticsearch.xcontent.XContentType;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Function;
import static org.elasticsearch.index.seqno.SequenceNumbers.UNASSIGNED_PRIMARY_TERM;
/**
 * Helper to parse bulk requests. This should be considered an internal class.
 */
public final class BulkRequestParser {