Add integration tests for status server

[robert-bell]

What you would like to be added?

Add integration tests for the status server handleTrainJobRuntimeStatus handler.

The tests should check include coverage of:

• the happy path (updating the train job status)
• invalid data is rejected with a useful error message (e.g. progressPercentage greater than 100)
• updating a non-existing trainjob is rejected with a useful error message

Why is this needed?

Improved test coverage will help us maintain this feature.

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[digvijay-y]

I would like to work on this.

[robert-bell]

Thanks @digvijay-y! Feel free to assign it to yourself with a comment / assign.

I'm very happy to help with the review.

[digvijay-y]

/assign