hdfs: Use logger rather than print statements

I tested this by running the following on a hdfs-configured machine:

    import luigi.hdfs
    import luigi.interface

    luigi.interface.setup_interface_logging()

    pipe = luigi.hdfs.HdfsAtomicWritePipe('my_file')
    pipe.writeLine('Hello')
    pipe.abort()
    pipe.writeLine('world')
    pipe.close()
Merge pull request #457 from Tarrasch/use-logger-not-print

hdfs: Use logger rather than print statements