[#52370535] Change ami to use new version

Pivotal tracker story [#52370535](https://www.pivotaltracker.com/story/show/52370535)

Reduced mongo usage from 2GB to 256mb. Winning.
Currently mongo is using journal files, which are using 2GB. Mongo partition has 3GB in total, which means that after we don't delete 4 dbs from tests it doesn't work any more.

Change mongo settings to use smaller journal files:

http://docs.mongodb.org/manual/reference/configuration-options/#smallfiles