Fix RELEASE_HOST config for release-hatch deployment

[bloodearnest]

RELEASE_HOST is wrongly set to http://localhost:8001 for the test-backend, which means all requests from job-server fail to validate.

Changing this to https://test.opensafely.org fixes the issue, however it breaks the functional test in release-hatch, as that was written to assume localhost. So release-hatch's functional test client needs to be able to a take a RELEASE_HOST argument, and then we can update the test here to use it.

[sebbacon]

Thanks for the write-up. What is the effect, on which kinds of end-users, of this misconfiguration?

[bloodearnest]

It means that the `view level 4 outputs' button on job-server, will not work for the backend, it will show empty filelist and a 403

[bloodearnest]

stupid comment button

[sebbacon]

This is still current, right? Is it important enough to get into Regatta?

[bloodearnest]

Probably not, it's a test framework fix, so would be good but probably not essential

[madwort]

is this fixed by #49 ?