Evaluation GET API ignores namespace value

### Nomad version
1.3 beta

### Operating system and Environment details

MacOS

### Issue

When getting a single eval at /v1/evaluation/ID, if you pass in a bad namespace, it still returns an evaluation.

### Reproduction steps

Call the evaluation API with a non-matching namespace value, like so:

`nomad operator api -verbose -namespace="BAD_NAMESPACE_VALUE" /v1/evaluation/dc5ba85c-7aa3-df14-7ba8-4d5319a67bd5 | jq`

#### Expected Result

The evaluation should only be returned if it is in the given namespace.

#### Actual Result

The evaluation will return regardless of namespace


Start at the GET /v1/evaluation/ID API endpoint and reproduce the issue with the provided nomad operator api command using a non-matching namespace. Trace how the namespace is handled for a single evaluation; done means the evaluation is returned only when it belongs to the requested namespace.

Written by the indexing model from the issue text.