Workers at a second Seattle Starbucks location have joined the nationwide wave of unionization at the coffee giant — this time at one of the company’s flagship roastery locations. Employees at the Starbucks Reserve Roastery, at Pike Street and Melrose Avenue in the Capitol Hill neighborhood, voted 38-27 to unionize with Workers United, an affiliate of the Service Employees International Union. About 100 workers were eligible to vote, and three ballots were challenged. The National Labor Relations Board announced the vote count Thursday. The vote shows “we’re really just hitting the gas with th…