ModulesService#getVersionHostname causes pipelines to fail often

[paradoxengine]

Hi,
we are seeing a number of cases where Pipelines seem to die because their tasks fail (and thus hit the max failuires in the queue). The main offender seems to be calls to ModulesService#getVersionHostname, which are done for each task instead of being set pipeline-wide.
Seems like a similar change (i.e. calling once per pipeline) has been implemented in mapreduce2 already.

We are using the Java version.

[tkaitchuck]

Good idea. It's probably also worth calling it from retry helper.
Feel free to send a pull request.