Iran's bad debt push reveals problem, and silver lining

* Push against defaulters reveals \"critical\" hole for banks * Loan problem is test for Rouhani's bid to boost economy * More cooperative mood may raise pressure for solution * Creditors include figures with likely ties to previous govt By Michelle Moghtader DUBAI, May 8 (Reuters) - A move by Iran to recover bad debts on behalf of banks has shed light on possible corrupt lending under the