INDIANAPOLIS — An Indianapolis-based liquor store chain wants to intervene in a federal lawsuit filed by gas stations and other businesses seeking to overturn a state law banning them from selling cold beer. Attorneys for 21st Amendment have filed a motion seeking to intervene in the suit filed in May by the Indiana Petroleum Marketers and Convenience Store Association and several store owners. The 19-store chain’s motion says that if a federal judge in Indianapolis overturns Indiana’s ban …