ChunkServerManager,BlockMapping and block is not strong-consistent

1. consistency problem between ChunserverManager and BlockMapping
2. ChunkServerManager和BlockMapping的一致性
之前有问题（在AddBlock是更新了后者，没更新前者，前者是在BlockReport时更新的，这就导致在report这个block前，chunkserver挂掉，那这个block不会DeadCheck被恢复，更严重的是Blockmapping却认为这个block的replica是存在的，等另一个chunkserver挂掉时，将它拿去做PullBlock的源地址了。

Start by tracing how AddBlock updates BlockMapping and ChunkServerManager, then compare the BlockReport, DeadCheck, and PullBlock paths described in the issue. Reproduce the failure scenario where a chunkserver stops before reporting a block, and define completion as keeping replica state consistent so recovery and source selection do not use stale information.

Written by the indexing model from the issue text.