BOOKKEEPER-623: LedgerChecker should avoid segments of closed ledger with higher start entryId than closed entry. (vinay via sijie)

git-svn-id: https://svn.apache.org/repos/asf/zookeeper/bookkeeper/trunk@1496705 13f79535-47bb-0310-9956-ffa450edef68
BOOKKEEPER-633: ConcurrentModificationException in RackawareEnsemblePlacementPolicy when a bookie is removed from available list (vinay via sijie)

git-svn-id: https://svn.apache.org/repos/asf/zookeeper/bookkeeper/trunk@1496706 13f79535-47bb-0310-9956-ffa450edef68