In a dramatic temporary reversal of policy, the Federal Housing Administration is giving condo buyers a much-needed break.Last week, the FHA, the federal agency that insures low-down-payment home loans for private lenders, said it was relaxing its building underwriting guidelines as a way of helping the struggling sector ride out the downturn. The move could help boost sales in condos by making more FHA mortgages available to borrowers.FHA loans provide qualified . . .