Use -p in hadoop mkdir

E.g. `hadoop fs -mkdir -p <path>`. Otherwise the mkdir will fail since the temp directory path hasn't been created, like:

```
STDERR: mkdir: `hdfs:///user/sjpaavol/tmp/mrjob/jobs.sjpaavol.20140127.092439.798924/files/': No such file or directory
./job1.py: ERROR: STDERR: mkdir: `hdfs:///user/sjpaavol/tmp/mrjob/jobs.sjpaavol.20140127.092439.798924/files/': No such file or directory
```