By Eduardo Baptista and Martin Quin Pollard BEIJING (Reuters) – President Xi Jinping, conspicuously absent from the main stage of diplomacy during China’s COVID isolation, has been mostly smiles and handshakes on his return this week with a flurry of meetings that Beijing hopes will begin to mend frayed relations. But in an exchange that went viral, a mask-less Xi was also captured on-camera giving Canadian Prime Minister Justin Trudeau a dressing-down at the Group of 20 (G20) summit over media leaks, apparently from their bilateral meeting a day previously. It was a rare, candid glimpse of th…