Master OOM when SplitTableRegionProcedure new CacheConfig and instantiate a new BlockCache

In our cluster, we use a small heap/offheap config for master. After HBASE-21290, master doesn't instantiate BlockCache when it not carry table. But it will new CacheConfig in SplitTableRegionProcedure.splitStoreFiles method. And it will instantiate a new BlockCache if it not initialized before and make master OOM.