Fix encoding and user problems in the Perforce unit tests.
Fix encoding and user problems in the Perforce unit tests.

The Perforce unit tests didn't work if your local user account wasn't
registered on public.perforce.com. We didn't notice because ours were
all on there, but this probably failed for some contributors and
certainly for continuous integration.

Along with this, the encoding wasn't explicitly set and, client-side,
was defaulting to "utf8" on newer versions of p4python. This wasn't
compatible with public.perforce.com.

We now explicitly set the user "anonymous" and encoding "none" in order
to ensure tests will pass.

Testing Done:
Successfully ran the Perforce unit tests locally and in CI.

Reviewed at https://reviews.reviewboard.org/r/8803/

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