Associating pipelines with environment specs do not clean up the pipelines they trigger

[chadlwilson]

https://github.com/gocd/ruby-functional-tests/blob/master/specs/AssociatingMultiplePipelinesWithAnEnvironment.spec and https://github.com/gocd/ruby-functional-tests/blob/9ab328e6efafa1e4752f48f19d8753ee9d584f35/specs/AssociatingAPipelineWithAnEnvironmentWithNoAgents.spec

Both trigger pipelines but do not cancel them or wait for completion. This can cause later specs to fail as pipelines are running that should not be running, causing timeouts and confusion.

Ideally we’d have a standard cleanup after every spec file, but short of that the scenario needs to clean up after itself.