By Lucia Mutikani WASHINGTON (Reuters) – U.S. job growth slowed moderately in September while the unemployment rate dropped to 3.5%, pointing to a tight labor market which keeps the Federal Reserve on its aggressive monetary policy tightening campaign for a while. Though the decline in the jobless rate from 3.7% in August was partly because of people leaving the workforce, fewer Americans worked part-time for economic reasons last month, the Labor Department’s closely watched employment report showed on Friday. The labor market continues to show resilience despite the Fed’s stiff interest rate…