Stir first 6 ingredients in heavy large saucepan over medium heat until sugar dissolves and mixture boils. Add rhubarb, currants, and green onions; bring to boil. Reduce heat and simmer until rhubarb is tender but not falling apart, about 4 minutes. Cool to room temperature. Discard cinnamon. Cover and refrigerate chutney until cold, at least 1 hour. (Can be made up to 2 days ahead. Keep refrigerated.) Bring to room temperature before serving.
