public static HiveClientCacheKey fromHiveConf(HiveConf hiveConf, final int threadId) throws IOException, LoginException {
      return new HiveClientCacheKey(hiveConf, threadId);
    }
A class to wrap HiveConf and expose equality based only on UserGroupInformation and the metaStoreURIs.
This becomes the key for the cache and this way the same HiveMetaStoreClient would be returned if
UserGroupInformation and metaStoreURIs are same. This function can evolve to express
the cases when HiveConf is different but the same hiveMetaStoreClient can be used
metastore/src/java/org/apache/hadoop/hive/metastore/HiveClientCache.java