By Steve Scherer OTTAWA (Reuters) -Canada's ruling Liberal Party won two of four seats up for grabs in by-elections to fill empty spots in the House of Commons, and performed better in a riding won by rival Conservatives than in 2021, preliminary results showed on Tuesday. Liberal Prime Minister Justin Trudeau won resounding victories for the Notre-Dame-de-Grace-Westmount seat in Montreal - where Conservatives came in third - and Winnipeg South Centre in Manitoba, and clawed back some 10 percentage points in the traditionally Conservative riding of Oxford, Ontario, versus the 2021 vote. This w...