Nomad UI Exec namespace issues

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Nomad version

Output from nomad version
0.12.5+ent

Operating system and Environment details

Debian 9.12

Issue

It looks like the Nomad UI does not support the exec UI for namespaced jobs.
When I browse to a job running in a namespace, then to a task or allocation for that job, clicking the 'Exec' button pops open a window saying "Not Found". Inspecting the JS console for this window, I see that it is attempting to fetch the job from the api, but without the namespace parameter. Note that if I use the exec button from the Job or task group UI, the namespace parameter is passed to the popup window and the exec UI works correctly

Reproduction steps

1. Launch a namespaced job
2. Browse to the allocation or task view for the job
3. Use the UI to try to exec to it

Reproduce the issue by opening a namespaced job's allocation or task view and using the Exec button. Inspect the popup's JavaScript console and API request, then verify that the namespace is included and the exec UI works for the namespaced job.