OSLO (Reuters) -Norway’s largest private sector labour union said on Wednesday it would later this month start blocking transit shipments of Tesla cars meant for the Swedish market, as part of a growing Nordic movement to support striking mechanics in Sweden. Swedish unions led by IF Metall have taken industrial action against Tesla since October to try to force the U.S. electric vehicle maker to sign collective bargaining agreements with mechanics. Dockworkers in Sweden already refuse to unload Tesla cars arriving by ship, and broad groups of Swedish electricians, cleaners, postal workers and…