fix(client): encode unicode properly for apps:run

I reviewed the deis.py client code as well but didn't see other instances where `encode()` was required to handle unicode input or output.

Closes #2801.
Actually the final `expect` string param to `utils.Execute` is ignored if the previous param is `false`. (Yes, this test code could be improved.) So it's basically testing that we don't see an error, which I think is sufficient here, but I'll change it to use `utils.CheckList` which should test and validate.