By Alastair Macdonald and Adrian Croft RIGA (Reuters) - European Union leaders met six ex-Soviet neighbors on Thursday in Riga, rejecting Russian "bullying" in the 18 months since their last summit in a once Kremlin-ruled EU capital sparked conflict in Ukraine. "The European Union stays the course despite the intimidation, the aggression, even the war, of the last year," said summit chair Donald Tusk.