Finish update before enqueueing worker

[zwolf]

The AggregationCompletedMailerWorker is sending failure emails for successful runs. Instead of passing a block to super, the AggregationsController should finish the update first so that the resource has its new status saved before enqueueing the mailer. Also, let's assume params are strings in the specs.

Review checklist

• First, the most important one: is this PR small enough that you can actually review it? Feel free to just reject a branch if the changes are hard to review due to the length of the diff.
• If there are any migrations, will they the previous version of the app work correctly after they've been run (e.g. the don't remove columns still known about by ActiveRecord).
• If anything changed with regards to the public API, are those changes also documented in the apiary.apib file?
• Are all the changes covered by tests? Think about any possible edge cases that might be left untested.