Insight - U.S., Iran keep Iraqi PM in place as he challenges ruling elite

By Stephen Kalin and Maher Chmaytelli BAGHDAD (Reuters) - The United States and Iran have formed an unlikely tacit alliance behind Iraq's prime minister as he challenges the ruling elite with plans for a non-political cabinet to fight corruption undermining the OPEC nation's economic and political stability. Local calls for Haider al-Abadi's removal -- including one by his predecessor as prime minister Nuri al-Maliki -- had been growing as he pursued a reshuffle aimed at addressing graft, which