By Pete Schroeder and Dhara Ranasinghe LONDON/WASHINGTON, Nov 15 (Reuters) - U.S. stock market investors shook off inflation jitters in early trading Monday, sending equities higher while oil slipped. Austria slapped a lockdown on people unvaccinated against the coronavirus on Monday as infections rose across Europe, with Germany considering tighter curbs and Britain expanding its booster programme to younger adults. Persistent supply chain bottlenecks and soaring energy costs are slowing euro zone growth and will keep inflation high for even longer than had been thought, European Central Bank chief Christine Lagarde said on Monday.