According to published reports, environmental activists will file a lawsuit seeking to expedite federal action on its request to give endangered species protection to the eastern diamondback rattlesnake.  This week, the Arizona-based Center for Biological Diversity and others filed a formal notice of intent to sue the U.S. Fish and Wildlife Service.    The groups contend that rattlesnake is threatened by loss of habitat and human predation across the Southeast, citing the fact that there are no bag limits in Florida, Georgia, Mississippi, Alabama, Louisiana or South Carolina.  The USFWS has indicated that action on the request would take years in that they are currently reviewing nearly 400 other species due to prior lawsuits filed by the Center.