Remove hardcoded auth options in common/auth.
Remove hardcoded auth options in common/auth.

They are now passed from outside everywhere. Related to issue #25.

R=iannucci@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2669933004

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go