HDFS-4782: code review feedback, getting code closer to matching branch-1
HDFS-4782: additional work to get FSEditLog.java into agreement with branch-1
HDFS-4782: whitespace
HDFS-4782: change DFS_NAMENODE_EDITS_TOLERATION_LENGTH_DEFAULT as per HDFS-3540
HDFS-4782: match imports to branch-1 version in TestCheckpoint
HDFS-4782: also including HDFS-3596 changes
HDFS-4782: whitespace