GLOBAL MARKETS-Europe holds nerve as Russia-Ukraine warnings ratchet up

* European markets shrug off rising concern about Ukraine/Russia * Euro steady after touching 1-yr low versus dollar in Asia * Official China manufacturing data underscores cooling fears * U.S. markets closed for Labor Day holiday By Marc Jones LONDON, Sept 1 (Reuters) - European markets cautiously set aside warnings that Russia's conflict with Ukraine was sliding out of control on Monday, as investors focused on the European Central Bank's meeting this week and hopes it wil