casper: Fix buggy waiting logic in 08-edit.

Apparently, this test was not allowing the browser to run between the
keypress to start edit and checking to see if message_edit_content appeared.

I'm not sure if this is what has been causing recent flakes, but it
was definitely wrong Casper code.

frontend_tests/casper_tests/08-edit.js

@@ -106,6 +106,9 @@ casper.then(function () {
     casper.waitUntilVisible(".message_edit_notice", function () {
         common.keypress(37);
     });
+});
+
+casper.then(function () {
     casper.waitUntilVisible(".message_edit_content", function () {
         var fieldVal = common.get_form_field_value('.message_edit_content');
         casper.test.assertEquals(fieldVal, "test edited pm", "Opened editing last own message");