personnes: datepickers' buttons properly rendered

Closes #3936

calebasse/static/js/calebasse.absences.js

@@ -32,6 +32,8 @@ function action(url, worker, on, action, selector, original_color, highlight_col
                 }
                 ).done(on_success)
               }}]});
+            $('form .datepicker input').trigger('focus');
+            console.log('dialog loaded');
         })
 };