When a shard becomes search active then trigger a refresh instead of waiting for the next scheduled refresh.
The `IndexShard#awaitShardSearchActive(...)` method registers a refresh listener and then often waits for the refresh scheduler to trigger a refresh. By default this is one second. In order to avoid increasing the query time of the Search API, the mentioned method should trigger a refresh instead for waiting it to happen.

As part of this change we also need to disable the refresh scheduler completely. Otherwise we run at risk of running two refreshes next after each other. One triggered from making shard search active and one from the refresh scheduler.  



server/src/main/java/org/elasticsearch/index/shard/IndexShard.java
} else {
                if (state != IndexShardState.CLOSED) {
                    logger.warn("Failed to perform engine refresh", e);
                }
            }
        } else {
            if (state != IndexShardState.CLOSED) {
                logger.warn("Failed to perform engine refresh", e);
            }
        }
    }
    /**
     * Called when our shard is using too much heap and should move buffered indexed/deleted documents to disk.
     */
    public void writeIndexingBuffer() {
        try {
            Engine engine = getEngine();
            engine.writeIndexingBuffer();
        } catch (Exception e) {
            handleRefreshException(e);
        }
    }
    /**
     * Notifies the service to update the local checkpoint for the shard with the provided allocation ID. See
     * {@link ReplicationTracker#updateLocalCheckpoint(String, long)} for
     * details.
     *
     * @param allocationId the allocation ID of the shard to update the local checkpoint for
     * @param checkpoint   the local checkpoint for the shard
     */