NN now tracks replicas by storage, so BlockInfo#findDataNode can be replaced with BlockInfo#findStorageInfo.
BlockManager#reportDiff is being fixed as part of HDFS-5483, this Jira is to fix the rest of the callers.
[suggested by sirianni on HDFS-5483]
Code cleanup of BlockInfo and rename BlockInfo to BlockInfoContiguous
NN should gracefully handle multiple block replicas on same DN