By Erin Murphy, Gazette-Lee Des Moines BureauDES MOINES — The one thing state troopers, teachers and workers at correctional and mental health facilities have in common is that they all are public employees.If Gov. Terry Branstad gets his way, they will have something else in common: a single health insurance program.It’s commonly called a master contract, and it’s one of the changes Republicans, with their newfound control of the state’s lawmaking process, are considering — along with perhaps larger changes in how or if public employees can collectively bargain for their wages and benefits.Representatives of some of those public employees say such a one-size-fits-all approach would have an adverse effect on employees and employers alike.Branstad signaled his desire for a master health insurance contract shortly after the Nov.