Speed up travis builds by distributing the deploys among the workers

The 6 workers now have the following responsibilities:

```
# 1. Deploy to sonatype (old hadoop)
# 2. Deploy to dopa (old hadoop)
# 3. Nothing
# 4. deploy to sonatype (yarn hadoop)
# 5. deploy to dopa (yarn hadoop)
# 6. Nothing
```
Especially worker 1. (which is always running out of time) does not need to download, build and upload the yarn stratosphere version.
This is done by worker 5 which has to download the yarn dependencies anyways.

I also changed the `ReOpenableHashTableITCase` to re-open the HashJoin from 5 to 3 times (the test case takes the most time)