Figure out a better way of resetting the environment between scenarios

[danielbachhuber]

Currently, if a scenario performs any form of database operation, the database alteration persists between scenarios. In the future, when the test suite is more comprehensive, this could cause unexpected failures when conflicts happen between scenarios.

We should figure out a better way of resetting the environment between scenarios. And, in the interim, we should make sure our scenarios clean up whatever database alteration they perform.

[stevector]

Drupal's Behat extension does some form of cleanup between scenarios. I know nodes get deleted at least. But it doesn't wipe the DB entirely. Over in the repo for the Drupal 8 search module I've been working on I rely on the config done in early scenarios persisting through to the final scenario: https://github.com/pantheon-systems/search_api_pantheon/blob/8.x-1.x/tests/behat/features/server.feature