hdfs healing reads
Running test for hdfs callback.
Use ram cache directly in Read. Run chksum and TTree::Draw().
Speedup Prefetch destruction by removing ram blocks from writing queue.
All working, but bad performace -- read and write simultanious.
Bugfix in GetNextTask - forgot to set task on exit.
Tagging v3.3.2
Tagging v3.3.1
Tagging v3.3.0
Tagging v3.3.0-rc3