Add guessable log stream name

[whyvez]

As a learn client running a task
I should be able to guess the log stream name
In order to connect to it and provide real-time logs to the user.

[whyvez]

@boriscosic will pass in AWS_LOGS_STREAM_PREFIX env var for pylearn/rlean loggers in the form of <scenarioID>-<command> i.e. scenarioabc-varsel

[whyvez]

@boriscosic We are currently adding a uuid suffix to the stream name. Once you start working with the CloudWatch API see if its easy to query based on prefix solely otherwise we can remove the suffix all together.

[boriscosic]

uuid at the time was just a way of randomizing the logs until we had a better system in place. I will pass in CW log stream name in the format <organization>-<dataset>-<scenarioId>-<command> so it corresponds to S3 path for that particular task.

[whyvez]

@boriscosic re. uuid suffix https://github.com/tesera/pylearn/blob/master/pylearn/__init__.py#L11

[jo-tham]

@boriscosic still need something here?