Add skiabot-ct-dm-003 to slave_hosts_cfg.py
Add skiabot-ct-dm-003 to slave_hosts_cfg.py

BUG=skia:4981

Review URL: https://codereview.chromium.org/1923223002

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