Automated tests for plugin installation on already deployed environment feature

We need to prepare test scenarios, to check if plugins can be installed after
deployment.

Scenarios to automate

1. Upload plugin to master node
2. Install plugin
3. Check if the plugin is installed
4. Check if the plugin can be assigned to existent environment
5. Adapt existent environment to the plugin (if needed) and assign the plugin
6. Check if the plugin started
7. Run network verification
8. Run OSTF