BAGHDAD — The U.S.-led coalition in Iraq withdrew on Sunday from a military base in the country’s north that nearly launched Washington into an open war with neighboring Iran. The K1 Air Base is the third site coalition forces have left this month, in line with U.S. plans to consolidate its troops in two locations in Iraq. A rocket attack on the base in late December killed one American contractor and lead to a series of tit-for-tat attacks between the U.S.