By Stephanie Nebehay GENEVA (Reuters) - The United Nations refugee agency called on Greece on Friday to take control of the "total chaos" on Mediterranean islands where thousands of migrants have landed. European Union member states must also do more to share the burden of Greece, where 50,000 people arrived in July alone, said Vincent Cochetel, UNHCR director for Europe, after visiting the Greek islands of Lesbos, Kos and Chios.