Improve test coverage for controller startup with conversion

[sbueringer]

Let's improve our test coverage as a follow-up to: #2321

The PR description describes the deadlock we encountered in detail. The following describes the test we need to ensure this doesn't happen again.

• Create a CRD with apiVersion v1
• Create CRs for this apiVersion
• Update the CRD to introduce apiVersion v2 (which should be also the new storage version)
• Setup a manager which:
  • implements conversion for this CRD
  • reconciles / watches the CRD
• Start the manager and ensure it works without a deadlock