Remove xml files and replace with ini style config in the hod.conf

No one likes xml. 

Depends on previous PR's.
For most examples we can reduce it to:
```
[Service]
ExecStart=hadoop-daemon.sh start datanode
ExecStop=hadoop-daemon.sh stop datanode
```
However, when we want to run MR1 we have to specify the appropriate path for scripts.

In any event, the proposed change is not a general solution, IMO.