Service plan uniqueness

[johha]

Are you submitting this PR against the develop branch?

👍

What is this change about?

A cc bug caused duplicated service plans in the response leading to errors e.g. during cf create-service. This change extends the existing service plan tests to ensure that the results are unique for regular users. To reduce code duplication the enable-service-access part was moved into a BeforeEach.

Please provide contextual information.

• https://github.com/cloudfoundry/cloud_controller_ng/pull/3648
• https://github.com/cloudfoundry/cli/issues/2792

What version of cf-deployment have you run this cf-acceptance-test change against?

v39.3.0

Please check all that apply for this PR:

• [ ] introduces a new test --- Are you sure everyone should be running this test?
• [x] changes an existing test
• [ ] requires an update to a CATs integration-config

Did you update the README as appropriate for this change?

• [ ] YES
• [x] N/A

How many more (or fewer) seconds of runtime will this change introduce to CATs?

N/A

What is the level of urgency for publishing this change?

• [ ] Urgent - unblocks current or future work
• [x] Slightly Less than Urgent