emulators.go: Change CockroachDB web UI's TCP port.
emulators.go: Change CockroachDB web UI's TCP port.

Currently the web UI is serverd on port 8080, but that's the same port at which we serve demo pages during development (both with Webpack and Bazel).

Bug: skia:11110
Change-Id: Ia0813a9e072c9c1cbec7592900effc243f3d429a
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/383740
Reviewed-by: Leandro Lovisolo <f558143c2568be8d55575d13f30a1fc5cb8009d5@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot