Most homeowners are satisfied that they got the best possible deal on their mortgages, results of a new Fannie Mae survey suggest. But the government-sponsored enterprise also found troubling levels of discontent among credit-impaired borrowers. Just 11 percent of subprime borrowers polled in the company’s annual survey said their lender offered them the best rate for which they qualified. Moreover, 15 percent of subprime borrowers said they chose a lender they thought approved most applications.