default boolean waitForCacheInitialization(long timeout) {
    return true;
  }
Wait for the block cache implementation to be completely enabled. Some block cache
implementations may take longer to initialise, and this initialisation may be asynchronous.
@param timeout time to wait for the cache to become enabled.
@return boolean true if the cache is enabled, false otherwise.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/BlockCache.java