Add retries to EMR provision/terminate tasks (and update ansible)

[pwnage101]

This commit is in response to a large volume of failed jobs that failed due to these ansible tasks failing (usually due to transient aws issues) but succeeded after manually retrying.

In order to complete this task, we also needed to update ansible from 1.4.4 to 2.5+.

DE-1483

Testing

I tested by running the debug-pipeline-job: http://jenkins.analytics.edx.org/job/debug-pipeline-job/288/console

The job failed because the task doesn't exist (FooBarDoesntExist) but the job otherwise has full coverage of the code changes in this PR.

[pwnage101]

Here are the docs that I read to help write this code:

• https://docs.ansible.com/ansible/latest/user_guide/playbooks_loops.html?highlight=retries#do-until-loops
• https://github.com/ansible/ansible/issues/20802#issuecomment-389190160

retries was added in 1.4, and we run 1.4.4. Unfortunately, the solution I implemented initially which was pulled from the latter link supposedly only works on 2.5+. I need to rework this since we run such an old ansible. Force-pushes incoming...

[brianhw]

Still LGTM. 👍

[pwnage101]

Confirmed that update-users still works: http://jenkins.analytics.edx.org/job/update-users/32/console

Merging.