### Description

Currently, the [`tryAuthenticateToken`](https://github.com/elastic/elasticsearch/blob/55088d154d1764a6d4fa8e9078bde9da1e9ff9a5/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/TokenService.java#L458) method calls `decodeAndValidateToken` which ends up sending two `GetRequest` for the same token ID. First in [`decodeToken`](https://github.com/elastic/elasticsearch/blob/55088d154d1764a6d4fa8e9078bde9da1e9ff9a5/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/TokenService.java#L602) and second in [`checkIfTokenIsValid`](https://github.com/elastic/elasticsearch/blob/55088d154d1764a6d4fa8e9078bde9da1e9ff9a5/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/TokenService.java#L1977). The second call is unnecessary as we already fetched the access token in the first call, it's just simply dropped. We should refactor these two methods to avoid sending second get request just to validate the access token.
x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/TokenService.java
*/
    public synchronized TokenMetadata getTokenMetadata() {
        return newTokenMetadata(keyCache.currentTokenKeyHash, keyCache.cache.values());
    }
    private static TokenMetadata newTokenMetadata(BytesKey activeTokenKey, Iterable<KeyAndCache> iterable) {
        List<KeyAndTimestamp> list = new ArrayList<>();
        for (KeyAndCache v : iterable) {
            list.add(v.keyAndTimestamp);
        }
        return new TokenMetadata(list, activeTokenKey.bytes);
    }
    /**
     * Refreshes the current in-use metadata.
     */
    synchronized void refreshMetadata(TokenMetadata metadata) {
        BytesKey currentUsedKeyHash = new BytesKey(metadata.getCurrentKeyHash());
        byte[] saltArr = new byte[SALT_BYTES];
        Map<BytesKey, KeyAndCache> map = Maps.newMapWithExpectedSize(metadata.getKeys().size());
        long maxTimestamp = createdTimeStamps.get();
        for (KeyAndTimestamp key : metadata.getKeys()) {
            secureRandom.nextBytes(saltArr);
            KeyAndCache keyAndCache = new KeyAndCache(key, new BytesKey(saltArr));
            maxTimestamp = Math.max(keyAndCache.keyAndTimestamp.getTimestamp(), maxTimestamp);
            if (keyCache.cache.containsKey(keyAndCache.getKeyHash()) == false) {
                map.put(keyAndCache.getKeyHash(), keyAndCache);
            } else {
                map.put(keyAndCache.getKeyHash(), keyCache.get(keyAndCache.getKeyHash())); 
            }
        }
        if (map.containsKey(currentUsedKeyHash) == false) {