Strorage-Client get list key report an error about nebula-java

[jerroldgao]

是不是Optional制定的时候没有制定默认值，NullPointerException是个trivial的问题。能不能更详细一点描述错误。

[zmh0531]

nebula-java/client/src/main/java/com/vesoft/nebula/client/storage/StorageClientImpl.java

Line 305 in 63403bc

threadPool.submit(() -> {

应该是线程池没有初始化，现在改好了。

还有这个计数器初始化数值是不是错了 应该是request.size吧

nebula-java/client/src/main/java/com/vesoft/nebula/client/storage/StorageClientImpl.java

Line 301 in 63403bc

final CountDownLatch countDownLatch = new CountDownLatch(groups.size());

[critical27]

groups是涉及到storage机器的数目，发到同一个机器的request会合并