Integration testing for RemoteRobotClient

[davidjsherman]

We need tests for the RemoteRobotClient zerorpc interface.

Even basic testing would have picked up #279 (comment), for example, since pypot.robot.remote.from_remote throws AttributeError immediately

[ymollard]

pypot misses a lot of tests in general. We're open to PRs on this topic :)
You may add new test files in the dedicated folder, run python -m unittest discover locally (it will discover all existing tests) so that they pass, and then open a PR. The CI will also run the tests before publishing.