ATLANTA — The water dispute between Alabama, Florida and Georgia is provoking hardball politics in Congress, where Georgia lawmakers derailed a proposal that could restrict metro Atlanta’s water supply. A provision initially tucked into a water projects bill would make it harder for metro Atlanta and North Georgia communities to take drinking water from two federal reservoirs. That restriction in early drafts of the 2013 Water Resources Development Act would effectively undermine a court decision affirming Atlanta can use one of those reservoirs, Lake Lanier, for its water needs, a legal victory for Georgia and a setback for Alabama and Florida.