Display dangling bosh variable references in ui when running browse

[rkoster]

Currently the following error message is shown.

> carousel browse                                                                                         
failed to update state got: credential not found for bosh variable id: 18d8a9f0-116e-44a3-b847-af8c0fea5434
run bosh deploy for 'snw-rmakkelie-lab-rabbitmq' so the BOSH director can converge it's variable references
exit status 1

However in cases like this just running a bosh deploy might not be what you want. So give carousel the ability to display inconsistent state, so the operator can make an informed decision on how to more forward.