Tenet Healthcare Corporation notified state regulators Thursday it was withdrawing its applications to buy five hospitals in Connecticut, ending a two-year effort by a national for-profit hospital chain to enter the changing Connecticut market. Its decision came 10 days after the state Office of Health Care Access proposed setting strict controls over staffing, services and pricing as a condition of approving Tenet's application to buy Waterbury Hospital and convert it from a non-profit to a for-profit institution. The withdrawal is a financial blow to struggling Waterbury Hospital and is likely to be a major political and fiscal complication for the administration of Gov. Dannel P. Malloy, the General Assembly and the city of Waterbury, where its two hospital are a crucial source of jobs.