(Reuters) - Residents of bankrupt San Bernardino, California on Tuesday voted to complete a rout of the city's pro-union old guard, electing business-friendly pragmatists who have pledged to try to reduce pension costs and take on vested interests. As San Bernardino enters into a fourth month of mediation with its creditors, the biggest of which is Calpers, California's giant retirement system, voters on Tuesday elected Carey Davis as the crisis-hit city's new mayor. Davis, a businessman and political novice, ran in part on a campaign to reduce the city's pension obligations. In an interview in November, when he became one...