webtry: Simply move sys/ directory into setup/.

That seems to make things more tied and that seems to be where we have
the same scripts/configs in the perf directory:
https://skia.googlesource.com/buildbot/+/master/perf/setup/sys/

That way we keep all files used/related to setting up a new webtry server in one place.

BUG=None
TEST=None
R=humper@google.com

Review URL: https://codereview.chromium.org/644513003