By Nick Tattersall and Tom Miles ISTANBUL/GENEVA (Reuters) - For a few days this week, officials in Turkey, Greece and Europe wondered if there might finally be signs of progress in their efforts to stem the flow of refugees and migrants pouring onto Lesbos. Only around 10 to 20 boats, each carrying some 50 tired and hungry people, have arrived on the Greek island in the past few days, far fewer than the thousands of people a day who had been crossing the narrow sea channel from Turkey just a few weeks earlier. Rougher waters were deterring migrants from attempting the journey, locals and aid workers said.