Couple of Netty fixes
a. Fix the port number by reading it from the bound channel
b. Fix the shutdown sequence to make sure we actually block on the channel
c. Fix the unit test to use two JVMs.
Flush serializer to fix zero-size kryo blocks bug.
Also convert the local-cluster test case to check for non-zero block sizes
Skip fetching zero-sized blocks in OIO.
Also unify splitLocalRemoteBlocks for netty/nio and add a test case
Also flush serializer in revertPartialWrites
Merge pull request #628 from shivaram/zero-block-size

Skip fetching zero-sized blocks in NIO.
Merge branch 'master' of git://github.com/mesos/spark

Conflicts:
	core/src/test/scala/spark/ShuffleSuite.scala
Merge pull request #627 from shivaram/master

Netty and shuffle  bug fixes
fix block manager UI display issue when enable spark.cleaner.ttl