Let's rename the various "processIOError" methods to be more descriptive. The current code makes it difficult to identify and reason about bug fixes. While we're at it let's remove "Fatal" from the "Unable to sync the edit log" log since it's not actually a fatal error (this is confusing to users). And 2NN "Checkpoint done" should be info, not a warning (also confusing to users).
HDFS-1073 these issues don't exist on trunk or 23.