Fix launcher tests for running on the 5.1 API on VCloud Director 5.5

In Vcloud Director 5.5 the API around a VM's hard disk capacity has changed, even when requesting the 5.1 API. We've fixed the problem in VCloud-Walker (https://github.com/alphagov/vcloud-walker/pull/61), but we also need to change a test so it can continue to assert on the correct data. 

* also added a git ignore for files generated by the acceptance tests