Add tests for remote single label classifier

[j-chim]

Description

Tested remote inference for single label classifier with and without encryption https://github.com/OpenMined/SyferText/issues/179.

Affected Dependencies

N/A

Checklist

• [x] I have followed the Contribution Guidelines and Code of Conduct
• [x] I have commented my code following the OpenMined Styleguide
• [x] I have labeled this PR with the relevant Type labels
• [ ] My changes are covered by tests

[j-chim]

@AlanAboudib I've incorporated your feedback in the latest commit. Will add tests for different access cases in the next PR