Hadoop in Azure stuck in ACCEPTED state

I ran

```
./pkb.py --cloud=Azure --benchmarks=hadoop_terasort
```

When the script finally reached the point in which it invokes `yarn` to run TeraGen, it got stuck for hours wating it to end.

I logged via ssh in the master machine and used `yarn` to discover that, the TeraGen application was ACCEPTED but still not RUNNING after 11hours.

No idea about what the issue could be. Insufficient memory? Which instance type is required as minimum to run this benchmark? By default `pkb` uses Small, which translates into A1-Standard (1 Core, 1.75Gb RAM)