Federal Protective Service contract guards failed to detect guns, knives and other prohibited items brought into federal agencies more than half of the time during covert tests by the agency, the Government Accountability Office reveals in a new report. Sen. Joe Lieberman, chairman of the Senate Homeland Security and Governmental Affairs Committee, said the new report shows FPS continues to face widespread problems with its contractor workforce. While it has taken some steps forward in recent months, the Federal Protective Service continues to be an agency in crisis. As I blogged earlier, the House Homeland Security Committee, which requested the…