CHANGES for HDFS-347 branch.
These will be integrated to trunk CHANGES.txt after merge


HDFS-4353. Encapsulate connections to peers in Peer and PeerServer classes.
(Colin Patrick McCabe via todd)

HDFS-4354. Create DomainSocket and DomainPeer and associated unit tests.
(Colin Patrick McCabe via todd)

HDFS-4356. BlockReaderLocal should use passed file descriptors rather than paths.
(Colin Patrick McCabe via todd)

HDFS-4388. DomainSocket should throw AsynchronousCloseException when appropriate.
(Colin Patrick McCabe via todd)

HDFS-4390. Bypass UNIX domain socket unit tests when they cannot be run.
(Colin Patrick McCabe via todd)

HDFS-4400. DFSInputStream#getBlockReader: last retries should ignore the cache
(Colin Patrick McCabe via todd)

HDFS-4401. Fix bug in DomainSocket path validation
(Colin Patrick McCabe via todd)

HDFS-4402. Some small DomainSocket fixes: avoid findbugs warning, change log level, etc.
(Colin Patrick McCabe via todd)

HDFS-4418. increase default FileInputStreamCache size (todd)

HDFS-4416. Rename dfs.datanode.domain.socket.path to dfs.domain.socket.path
(Colin Patrick McCabe via todd)

HDFS-4417. Fix case where local reads get disabled incorrectly
(Colin Patrick McCabe and todd via todd)

HDFS-4433. Make TestPeerCache not flaky (Colin Patrick McCabe via todd)

HDFS-4438. TestDomainSocket fails when system umask is set to 0002. (Colin Patrick McCabe via atm)

HDFS-4440. Avoid annoying log message when dfs.domain.socket.path is not set. (Colin Patrick McCabe via atm)

HDFS-4473. Don't create domain socket unless we need it. (Colin Patrick McCabe via atm)

HDFS-4485. DN should chmod socket path a+w. (Colin Patrick McCabe via atm)

HDFS-4453. Make a simple doc to describe the usage and design of the shortcircuit read feature. (Colin Patrick McCabe via atm)

HDFS-4496. DFSClient: don't create a domain socket unless we need it (Colin Patrick McCabe via todd)