The Twins have designated righty Jharel Cotton for assignment, tweets Betsy Helfand of the St. Paul Pioneer-Press. The move is made in preparation for the activation of Bailey Ober from the 60-day injured list, which is expected to be finalized tomorrow. Cotton is no stranger to DFA limbo, as he’s been on and off the Minnesota roster all year. Claimed off waivers from the Rangers over the offseason, the 30-year-old opened the year on the active roster but was DFA a week into the season. He cleared outright waivers and accepted an assignment to Triple-A St. Paul, kicking off a…