By Julien Ponthus LONDON (Reuters) -Credit Agricole SA on Thursday posted a sharp fall in first-quarter profit as it took more than half a billion euros in provisions against its exposure to Russia and Ukraine. A disappointing reading for its capital ratios, higher than anticipated costs and better-than-expected performances from rivals, BNP Paribas and Societe Generale weighed on its shares in early Paris trade. France’s second-largest listed bank, also referred to as Casa, said net income fell 47.2% to 552 million euros ($586 million) after it took the decision to make a “conservative” assum…