Always include gpu dimension in bot dimensions
Always include gpu dimension in bot dimensions

This way we'll be able to explicitly request
swarming bot with no special GPU.

BUG=chromium:426897
R=maruel@chromium.org

Review URL: https://codereview.appspot.com/165770043

luci/luci-py,pombreda/swarming,luci/luci-py,pombreda/swarming,madecoste/swarming,madecoste/swarming,pombreda/swarming,luci/luci-py,madecoste/swarming,luci/luci-py,pombreda/swarming,madecoste/swarming