By Elizabeth Pineau SARCELLES, France, June 2 (Reuters) - When Bassi Konate became mayor of Sarcelles this spring, the independent candidate backed by the hard-left France Unbowed (LFI) party ended three decades of municipal rule by the Socialists, the traditional powerhouse of the French left. A native of Sarcelles, a poor, multi-cultural town north of Paris, Konate, 38, leveraged his hometown roots and a network of rappers, soccer stars and influencers to mobilise young voters through social media and canvassing.