By Andrew Gray ANKARA, July 8 (Reuters) - Disputes between U.S. President Donald Trump and other NATO leaders showed the alliance's democratic strength and should serve as a lesson for Russian President Vladimir Putin, NATO Secretary General Mark Rutte said on Wednesday after a summit in Ankara. In an interview with Reuters, Rutte also said he saw no need to change the way he deals with Trump, despite accusations that he lavishes praise on the U.S. president and fails to push back on his critici