PARIS — Paris was plunged into panic — again — when soldiers guarding the Louvre Museum shot an attacker who lunged at them with two machetes on Friday and shouted "Allahu Akbar!" as the historic landmark went into lockdown. The threat appeared to quickly recede after the assailant was subdued, but it cast a new shadow over the city just as tourism was beginning to rebound after a string of deadly attacks. Coming just hours before Paris finalized its bid for the 2024 Olympics, it also renewed questions about security in the City of Light.