NEW YORK (Reuters) - U.S. mortgage rates rose for a fourth-straight week, Freddie Mac reported on Thursday, reaching a two-month high and again becoming a factor impeding traffic among rate-sensitive prospective home buyers.The average rate on a 30-year fixed-rate mortgage ticked up to 6.94% for the week ended Feb. 29 from 6.90% the week prior, the report said.“The recent boomerang in rates has dampened already tentative homebuyer momentum as we approach the spring, a historically busy season for homebuying. While sales of newly built homes are trending in a positive...