By Bansari Mayur Kamdar (Reuters) -UK shares shed their early gains to end lower on Monday, with tensions in Ukraine keeping global markets on edge. The FTSE 100 index closed 0.4% down, while the domestically focused mid-cap index declined 1.2% and hit a more than 11-month low. The office of French President Emmanuel Macron said on Monday U.S. President Joe Biden and Russian President Vladimir Putin had agreed in principle to a summit over Ukraine. But the White House said it had agreed to a meeting only “if an invasion hasn’t happened”, while the Kremlin said there were no concrete plans yet …