Introduce BookieClusterManager and Improve BookieListener

[sijie]

FEATURE REQUEST

1. Please describe the feature you are requesting.

• introduce BookieClusterManager class for managing the available/readonly/registered bookies in a centralized place (before that it was spread across different classes)
• improve BookieListener for listening on the topology changes. so the caller of listeners don't have to do this one-time notify actions.

2. Indicate the importance of this issue to you (blocker, must-have, should-have, nice-to-have). Are you currently using any workarounds to address this issue?

blocker

It is a basic change for sub-sequent changes that twitter did on auto-recovery.

3. Provide any additional detail on your proposed use case for this feature.

this change is contributed by @yzang

[sijie]

tag @yzang as the contributor.

[eolivelli]

Maybe this could be a good base for an abstraction from ZK, I will wait for the PR

[sijie]

@eolivelli this is just an attempt to improve the bookies management for auto-recovery, we are not touching the piece for clients. it is mostly for other changes that Twitter made in auto-recovery. Currently bookie watcher is untouched. so it is far from an abstraction for zookeeper.